- It uses heavy armor and has a very good health pool;
Most things with heavy armor proficiency also come with d10 or d12 HD. Barbarian’s d12 plus bonuses to Constitution while raging is the most you can get, obviously, but that doesn’t sound like a death knight and also barbarians don’t do heavy armor so well.
- Wields mid and short-ranged magic to compliment heavy melee blows;
This will be hardest; most magic-and-martial classes focus on using magic to buff yourself rather than to affect foes directly. Magus is probably the only real option here.
- Has some anti-magic utilities on its toolkit, in the form of creating a magic dampening area or shielding itself against magic attacks;
Well this is going to take some refluffing, because it simply doesn’t exist in Pathfinder outside of antimagic field—which affects all your magic too, and so it isn’t going to work. Maybe just having dispel magic?
That’s probably just going to be a matter of spell selection.
- Specializes in either Dual Wielding or Two-Handers, but not shields;
That’s definitely going to just be a matter of feat selection.
- Adept at using Frost Magic and Necromancy;
Again, probably just going to be about spell selection.
- May have an undead minion following it around;
Might be about spell selection, but could possibly something else.
- Can heal himself, but not others;
Uuuh... huh. Psychic warrior, maybe, if third-party material is allowed. There isn’t a lot of this kind of thing in Pathfinder to my recall.
- Can enchant its own weapon with some special effects;
I gather you mean temporarily, mid-combat. Magus again comes to mind, due to the arcane pool.
So, given all this, options:
Paizo Pathfinder
Note that each of the following are spellcasting classes: that makes them very awkward for dual-wielding, as they cannot easily hold two weapons and have a hand free for spellcasting. Two-handed weapons are not inconvenienced, though (except for the magus), since you can always just let go with one hand (a free action), cast the spell, and grab the weapon again (another free action).
Magus
Magus gets you spell combat, which is great, and arcane pool, which is directly relating to one of your points. It does not get heavy armor or a particularly-good health pool, and both two-handed weapons and two-weapon fighting are problems for magus.
There is a third-party arcane marauder archetype that works with two-handed weapons, it doesn’t get spell combat until 8th, which means I for one would never voluntarily play it at a level lower than that. Even then, it has diminished spellcasting for absolutely no good reason, because people seem to vastly overestimate the significance of two-handed weapons in Pathfinder and how big a deal it is to let a magus actually use them.
Aside from that, the character could just use a one-handed weapon, and use both hands for attacks outside of spell combat. As mentioned, it’s a free action to put a hand on or take one off. Still, that does mean not going with the biggest weapons.
Two-weapon fighting is just right out, for a magus.
For the armor, the arcane marauder does get medium armor from 1st, but then doesn’t get heavy armor at all. We can improve on that somewhat by looking at the deep marshal archetype, which could perhaps be tweaked to be less “dwarf-y” in general, and to keep necromancy and lose something else instead. Unlike arcane marauder, the deep marshal is quite strong, and I’d be happy to play that. It does fail to achieve heavy armor proficiency until 9th level, though, and does nothing about the magus’s average health pool.
About the health pool, the only option you’ve really got is Toughness, which is a shame because Toughness is a mediocre feat.
Also, officially, arcane marauder and deep marshal are incompatible—but this isn’t a difficult one to massage into place, however—ditch some of the arcane marauder’s weapon training for heavy armor magus, and if you’re keeping the concept of weapon restrictions on the deep marshal, make the list of allowed weapons be two-handed rather than one-handed to go with heavy spellstrike and heavy spell combat.
There’s no good way to enable self-healing on a magus, nor do they get animate dead or the like for undead allies, that that could easily be part of what the deep marshal adaptation gets instead of the official deep marshal’s list of “dwarfy” spells.
Warpriest
Heavy armor, any weapons you like, sacred weapon is there for that weapon-enchanting bit, and then fervor can back that up. They can definitely get undead companions, as well as things like frost and force choke, from the cleric spell list. That magic can be long-range, too, but you don’t have to choose it. They get shield proficiency, but don’t have to use it.
Healing they can do, but nothing prevents them from healing others—maybe use dhampir or the Tomb-Tainted Soul feat from the 3.5e Heroes of Horror supplement to heal from negative energy, and only prepare negative-energy-based spells for healing, so they don’t work on allies?
Again, HD is d8, not superb; Toughness can improve it but that is a painful feat tax as you generally want more from your feats than Toughness offers.
Dual wielding is hard for a spellcaster, though—you need a free hand. With a two-handed weapon (and without spell combat), it’s easy to just let go of the weapon with one hand, cast the spell, and put it back, but you cannot easily let go of one of your two weapons in a dual-wielding scenario.
There aren’t a lot in the way of relevant warpriest archetypes.
Antipaladin
The antipaladin has a strong case for some of the laziest design in Pathfinder—they couldn’t even be bothered to give it its own name—but it does check some boxes here. Heavy armor, d10 HD, strong connections to undeath. If the death knight themselves are undead, the touch of corruption and channel negative energy could even justify healing themselves and not others.
The Tomb-Tainted Soul feat from the 3.5e Heroes of Horror supplement can do the same for a living death knight, by giving them the healed-by-negative, hurt-by-positive trait of undead creatures. The same feature is also available from the knight of the sepulchre archetype, which slowly turns the antipaladin into the undead.
The fiendish boon can cover enchanting the weapon. Aura of cowardice and unholy resilience can be fluffed quite a lot like the magic-dampening aura you mentioned: spells are weaker against the antipaladin, and protections from fear magic work less well.
Cleric
Cleric is a good choice just because they get access to all the magic: necromancy, frost, antimagic, the works. They don’t get innate weapon skills (though they can get them, e.g. with divine power), and their HD is on the small side and they lack heavy armor proficiency. So in a lot of ways, several misses, though there’s a lot of upside.
The undead lord archetype exists, but honestly it’s not all that good–the undead companion you get from it is extremely lackluster. And it (well, it and a couple bonus feats) costs you a second domain, which is quite a price. If you really wanted those feats anyway, it’s probably worth it, but otherwise I’d pass.
Speaking of domains, undeath is pretty obvious, but Pathfinder bizarrely lacks much of anything in the way of cold or frost or winter themed cleric domains. There’s a third-party ice domain. Druids (but not clerics) get an arctic domain. 3.5e’s Spell Compendium has the cold domain, and its Frostburn supplement has the winter domain, but 3.5e domains worked differently. And Pathfinder itself, bizarrely, has nothing.
Death knights are also notable for disease effects. Alongside the undeath subdomain, there’s also the plague subdomain; you can’t have both, though. 3.5e’s Spell Compendium also has the pestilence domain, and its Fiendish Codex I has the corruption domain, but again 3.5e domains worked differently.
Dreamscarred Press Pathfinder
Dreamscarred Press is a third-party publisher for Pathfinder, and they have some stuff that may be of use to you. Note, however, that I have worked with DSP in the past (though not on anything I’m going to be recommending, in particular). I don’t know other third-party publishers as well, so I don’t have much in the way of suggestions for them.
None of the following are spellcasting classes, which mean none of them have the same troubles with dual-wielding while casting spells.
Psychic Warrior
The psychic warrior class hits a number of high points. It gets a magus-like ability to manifest powers while also making weapon attacks at 5th level, and it’s not required to have a hand free to do it. HD and BAB are average, but heavy armor is available.
The dervish path even enables dual-wielding, unlike all of the spellcasting classes above. Other paths like mind knight or weaponmaster are also very good.
Body adjustment enables actual, legit, self-only healing, without worrying about Tomb-Tainted Soul. Vampiric blade is also, I think you’ll agree, very much the right theme.
The big problem is that psionics does not do necromancy, at least in the zombie army sense. The psionic analogue to necromancy is athanatism, and it’s much more about manipulating spirits and souls to achieve effects than magical necromancy, and again, animating the dead is just right out.
War Mind
DSP’s war mind prestige class is a full-BAB, d10 HD class with powers similar to the psychic warrior, albeit without the warrior’s paths.
Harbinger
DSP also publishes Path of War, which is inspired by the 3.5e Tome of Battle supplement, and the harbinger has some pretty strong dark/necromantic themes. It’s also awkwardly a skirmisher with only light armor, but multiclassing can handle that well.
Path of War classes do not get spells, but they can, and the harbinger does, learn supernatural maneuvers, many of which are going to hit exactly the themes that a death knight wants: attacking and creating magical effects. And the Unquiet Grave discipline can be traded for one of the harbinger’s default disciplines to play up the necromancy angle.
D&D 3.5e feats
I already mentioned Tomb-Tainted Soul from Heroes of Horror a couple of times, but I want to mention it again: this feat makes a living character heal from negative energy and take damage from positive energy as if they were undead. Not only is this very thematic, it also goes a long way towards achieving “self-only healing” since the negative energy they use on themselves won’t be useful to their living allies.
In addition to that, there is the Lord of the Uttercold feat from Frostburn. This feat allows any cold-damage-dealing spell to instead deal damage that is half-cold, half-negative energy. Obviously very on-brand for a death knight.
Finally, Martial Study from Tome of Battle can get some of the excellent maneuvers from that book, even if you are not one of those classes. There are many great options, but I want to point out shadow garrote in particular, which a character qualifies to take at 10th level at the latest (it can be earlier by taking levels in initiating classes from that book or Path of War). Shadow garrote has you “create a strand of shadow that you hurl at an opponent. The strand wraps around the target’s throat and chokes it.” Thus making it the most direct example of a force-choke-like power available to my knowledge.
D&D 3.5e classes
Dread Necromancer
This class from Heroes of Horror doesn’t really hit too many high notes here; it doesn’t make much of a warrior and it doesn’t have a ton of cold magic either. What it does have, however, is charnel touch, an at-will negative-energy touch attack, which when combined with Tomb-Tainted Soul, is rather ideal for self-only healing. The 5th-level fear aura is also quite potent, and of course, dread necromancer is the class to beat when it comes to leading a zombie horde.
I also wrote an uttercold necromancer, which is a variant dread necromancer that focuses on cold and negative energy damage. Still not a great warrior, though you might combine it with other options like abjurant champion from Complete Mage or jade phoenix mage from Tome of Battle. Or perhaps tweak it to be divine-spellcasting, to combine with one of the prestige classes below:
Bone Knight
The Five Nations Eberron supplement for 3.5e includes the bone knight prestige class for the nation of Karrnath. A 4th-level paladin or antipaladin qualifies easily, as does a 6th-level cleric. It gets a skeletal steed, magical armor and later weapons made from bone, ability to control and animate the undead, and it advances divine spellcasting on all levels but 1st. Overall, a very strong class, and a very good choice here.
They also have the big d10 HD and all armor profiency. They also get shield proficiency (even tower shield proficiency), but that’s easily ignored (indeed, most bone knights should).
Prestige Paladin
3.5e’s Unearthed Arcana included a variant that had the paladin as a prestige class. In short, the advantage of prestige paladin is that all paladin spells are added to some other divine spellcasting class’s list—allowing you to combine paladin with, say, cleric.
Paladin of Slaughter
Up to you whether Unearthed Arcana’s variant-alignment paladins are even lazier than the antipaladin or not, but the paladin of slaughter massaged to be like the Pathfinder paladin is another good choice—mostly because aura of despair is a lot better than aura of cowardice.
If you apply the prestige paladin rules to the paladin of slaughter, and upgrade the smite to work like in Pathfinder, you get a rather powerful class.
Ruby Knight Vindicator
From Tome of Battle, the supplement that inspired Path of War, the ruby knight vindicator combines martial skills with divine spellcasting, and it is a very strong class. Its default fluff also involves worship of Wee Jas, lawful-neutral goddess of death, which feels right. Wee Jas doesn’t like people reanimating the dead that much... except for her own people.
Recommendation
2nd-level (anti)paladin/18th-level harbinger (3pp material)
The two levels of paladin of slaughter or antipaladin provide heavy armor proficiency and Cha to all saves, making the death knight very, very tough. Then harbinger provides all manner of powerful curse-and-darkness-oriented offense. Unquiet Grave plays up the necromancy. Probably my top choice.
8th-level cleric/2nd-level prestige (anti)paladin/10th-level bone knight (3.5e variant material)
A late-bloomer, to be sure, since heavy armor and martial weapon proficiency don’t happen until 7th level. Still, you get the best magic, and BAB +18/+13/+8/+3 in the end, as well as Cha-to-all-saves and a ton of undeath-themed abilities.
Cutting the variant Unearthed Arcana content is easy enough; the prestige paladin levels can be replaced with regular paladin levels, which can even replace the cleric levels (though magic will suffer badly), or just cut entirely, going with pure cleric/bone knight.
4th-level (anti)paladin/6th-level psychic warrior/10th-level war mind (3pp material)
The paladin of slaughter (or antipaladin) levels give enough necromancy and negative-energy channeling to enable the necromantic feel of the death knight, plus unholy resilience is very good, as is the paladin of slaughter’s aura of despair. The actual order of levels is awkward: you want the 6th level of war mind and martial power ASAP, but until you take some (anti)paladin levels, you’re not going to be very strong on the necromantic themes (though vampiric blade and the like can get part of the way there). In fact, if those are good enough, or nearly so, you might just play up necromancy with feats, or a single-level dip in cleric for negative energy channeling.
4th-level cleric/1st-level crusader/8th-level bone knight/7th-level ruby knight vindicator (3.5e material)
The cleric/crusader base is standard fare for ruby knight vindicator, but here we swap the last three levels of ruby knight vindicator in favor of bone knight, in order to hit the excellent exoskeleton of undeath feature. You’ll want to alternate levels of ruby knight vindicator and bone knight in order to maximize manuever levels—probably something like this:
\begin{array}{r l l c c}
\textbf{Lv} & \textbf{Class} & \textbf{Special} & \textbf{Spells} & \textbf{Maneuvers} \\ \hline
1^\text{st} & \text{Cleric} & \text{Domains} & 1^\text{st} & - \\
2^\text{nd} & & & 1^\text{st} & - \\
3^\text{rd} & & & 2^\text{nd} & - \\
4^\text{th} & & & 2^\text{nd} & - \\ \hline
5^\text{th} & \text{Crusader} & \text{Furious counterstrike,} & 2^\text{nd} & 2^\text{nd} \\
& & \quad\text{steely resolve} \\ \hline
6^\text{th} & \text{Bone Knight} & \text{Bonecraft armor} & 2^\text{nd} & 2^\text{nd} \\
7^\text{th} & & \text{Skeletal steed} & 3^\text{rd} & 2^\text{nd} \\ \hline
8^\text{th} & \text{Vindicator} & & 3^\text{rd} & 3^\text{rd} \\ \hline
9^\text{th} & \text{Bone Knight} & \text{Master of the white banner} & 3^\text{rd} & 3^\text{rd} \\
10^\text{th} & & \text{Nonlethal & stun immunity} & 4^\text{th} & 3^\text{rd} \\ \hline
11^\text{th} & \text{Vindicator} & \text{Divine recovery} & 4^\text{th} & 4^\text{th} \\ \hline
12^\text{th} & \text{Bone Knight} & \text{Fill the ranks 1/day} & 5^\text{th} & 4^\text{th} \\
13^\text{th} & & \text{Bonecraft weapon} & 5^\text{th} & 4^\text{th} \\ \hline
14^\text{th} & \text{Vindicator} & & 6^\text{th} & 5^\text{th} \\ \hline
15^\text{th} & \text{Bone Knight} & \textit{Medium fortification,} & 6^\text{th} & 5^\text{th} \\
& & \quad\text{fight while dying} \\
16^\text{th} & & \text{Exoskeleton of undeath} & 7^\text{th} & 5^\text{th} \\ \hline
17^\text{th} & \text{Vindicator} & & 7^\text{th} & 6^\text{th} \\
18^\text{th} & & \text{Armored stealth} & 8^\text{th} & 6^\text{th} \\
19^\text{th} & & & 8^\text{th} & 7^\text{th} \\
20^\text{th} & & \text{Divine impetus} & 8^\text{th} & 7^\text{th} \\
\end{array}
20th-level antipaladin (pure 1pp material)
Avoiding third-party material altogether, the antipaladin still seems choice here. It’s not everything you could ever want but it does hit a lot of high points. Knight of the sepulchre even achieves something like self-only healing.
