Ask the player.
First there is nothing wrong with making a mistake, we all do it, you will make more, don't try and hide it. You're the DM you are tracking a lot of stuff mishaps happen.
Just ask that player what they want to do, do it before the session even starts. Pull them aside, explain what happened, (they should be tracking the companions saves and ...
No, Drakes aren't Beasts
Drakes, though animal like in appearance and behavior, have the creature type of dragon, not beast. And the Ranger's Companion states:
Choose a beast that is no larger than Medium and that has a challenge rating of 1/4 or lower (PHB, p. 93 bold added).
"Beast" is not just a descriptive word here, it is a creature type (see ...
You don't need to homebrew a magic creature - just use the Find Familiar spell
Caleb's cat Frumpkin is pretty cool, and luckily you don't need to do any DIY work to have a similar creature in your game. Frumpkin is a familiar as summoned by the first level wizard spell Find Familiar, which summons some kind of spirit in the form of a beast, such as a cat or ...
Yes, if your DM thinks a panther has the right anatomy.
The gnome is Small (PHB 37) and the panther Medium (PHB 308). The relevant rule says:
A willing creature that is at least one size larger than you and that has an appropriate anatomy can serve as a mount (PHB 198)
Your ranger's animal companion is certainly willing. It does depend on whether your ...
Since someone answered what the DM should do and how he should think about the ranger's animal companion VS other, normal, beasts, let me tell you what I would do as a player since that's the actual question here.
I believe that a lot of the "fun of RP" (for lack of a better term) is up to the players. The DM is NOT the only one responsible for it, so there ...
The lowest-CR drake on D&DBeyond has CR = ½
A ranger's companion must have CR ≤ ¼.
So no, you cannot (currently) have a drake as your animal companion. To do so would require either a modification to the ranger rules or a new drake with CR ≤ ¼ (and the beast type, as gandalfmeansme rightly points out) to be published by WotC.
No, you can not choose a swarm
The simplest argument is that the Ranger must choose a beast, singular, not a swarm of beasts, plural. Jeremy Crawford even supports this interpretation (although in this case referring to Wild Shaping druids.)
Natural vs unnatural
There are also additional arguments to be made against a swarm being a valid option.
Good for your player -- he's recruited some temporary NPCs to help the group out!
Your header question asks how to "balance" this, but there's not a need for balance considerations since these NPCs are temporary. Your player will need to keep making checks to keep the guard drakes on his side.
You should have the guard drakes act on your rogue player's ...
What's important to you here, the fluff or the crunch?
"Fluff" is the game world that the DM describes and the players interacts with. "Crunch" is the actual game rules mechanics. For example, if you had a player who described their character as a lightly armored duelist fighter who specialized in the rapier, that's their fluff, while the crunch might be ...
Yes, a player should know their mount's exact HP.
It's so clear-cut that even if the rules clearly said otherwise, you would want to override them to work differently.
I have never yet seen a DM with enough bandwidth to manage all the things which they already need to keep track of (myself included) and every addition to that reduces the quality of DMing ...
You can't, because they don't meet the CR requirements.
In order for a beast to be chosen as a Ranger's companion, it must have a challenge rating of 1/4 or lower. While the form that a druid takes might be the form of a beast with a CR of 1/4, the CR of the druid itself will be much higher. Since the druid is not a beast with a CR of 1/4 or less, it can't ...
Since the Pseudodragon is still CR 1/4 I don't see there being too many problems with this. I don't think the creature's type is going to make any huge difference regarding balance or gameplay.
The main things that jump out at me from its stat block are that it can do extra poison damage on a save, but then so can the Giant Centipede, which is a CR 1/4 ...
By RAW, no. From page 93 of the PHB:
though the beast does not take any actions unless you command it to.
That much is pretty clear-cut.
By RAI, were it my game, I'd probably allow the beast to stand guard and engage with anyone who tries to harm the unconscious body of its master, but it would be under DM control and if I were using morale, that would ...
Barding. Barding is armor designed to protect an animal’s head, neck, chest, and body. Any type of armor shown on the Armor table in this chapter can be purchased as barding. The cost is four times the equivalent armor made for humanoids, and it weighs twice as much.
If you look at that description of Barding from the PHB, it can be reasoned that any animal ...
The DM and player can decide this together, and it'll differ based on the character of your game
Rules as written, there is no requirement to wait, or to be anywhere in particular, when the companion is granted. (This is true for abilities granted at levelling up in general, e.g. knowing new spells, or having an ability you didn't have yesterday.)
In more "...
No, it doesn't overpower the ranger
The core PHB ranger is generally held to be the weakest class in the game, even by the designers; such is noted in the article which published the UA Revised Ranger:
Over the past year, you’ve seen us try a number of new approaches to the ranger, all aimed at addressing the class’s high levels of player dissatisfaction ...
Not for the Beast Master Companion
The beast companion for that Ranger is granted by their class features. This makes it for all intents and purposes part of the Ranger (and included in their levels, as it were). In particular it uses their initiative and their actions to make attacks, meaning they are not an independent creature contributing to encounters. ...
Companion animals are like NPC's - they need personality as well as stats to shine.
When a player has an animal that's part of a class feature it's a character as much of the rest of the players - the flying cat won't be able to do much as the bard isn't trained to do anything with it, if anything it should act like a normal cat, sleep, run off, hide, etc.
Your eagle would effectively be mounting you
If your eagle lands on your shoulder, then so long as you are at least one size category larger than the eagle, the rules for mounts would come into play. To answer your questions directly, it wouldn't gain a bonus to AC, nor would you suffer a penalty to movement, but it would move with you on your turn without ...
This works by RAW
Nothing in RAW will prevent you from taking a Stirge as a companion. You would then be able to use your action to command it to attack exactly as you describe. Once attached, it would not require an attack to deal the damage each round. It would then take the Dodge action each round as per the errata.
I would rule that it can't Dodge
I'd use custom items to accomplish this. First is an item to allow your aquatic animal to walk:
Belt of Piscine Endowment
Aura faint transmutation; CL 5th
Slot belt; Price 30,000 gp; Weight 1 lb.
When above water, this belt seems to be made of sharkskin. When below water, it seems to be made of the skin of a furry mammal.
In 5th edition, it is as you have said. The animal will normally only act when commanded.
However, in the PHB Errata, it says:
Ranger’s Companion (p. 93). If you
are incapacitated or absent, your beast
companion acts on its own, focusing on
protecting you and itself. It never requires
your command to use its reaction, such as
when making an ...
Unless your DM explicitly creates houserules that allow you to make your companion into a familiar, no, there is no way to do this.
The Find Familiar spell lets a wizard
gain the service of a familiar, a spirit that takes an animal form you choose: bat, cat, crab, frog (toad), hawk, lizard, octopus, owl, poisonous snake, fish (quipper), rat, raven, sea ...
The beast scales decently in damage, but has poor survivability. The beast also prevents you from using some combat features, like TWF.
TWF = Two-Weapon Fighting
Looking at the 3rd level – when you get the beast – If you pick a Wolf, you will have a companion with +6 and advantage to hit, dealing 2d4 + 5 damage (10 on average), the only resource spent is ...
The 3rd level ability allows a Beast Master Ranger to "Choose a beast that is no larger than medium and has a challenge rating of 1/4 or lower" and "If the beast dies, you can obtain another one ..."
"Another one" means the same type of beast as the first i.e. no larger than Medium with CR 1/4 or less.
As an aside: the Beast Master Ranger is a relatively ...
It is too powerful.
A CR 1 creature is comparable to a level 3-4 PC. Giving the PC an entire new PC of similar level (roughly) is an extreme jump in power level, even considering the relative weakness of the archetype in other respects.
Consider making the dragon an ally rather than a companion
To avoid having the dragonborn and is companion outshine the ...
A Helm of Comprehending Languages will work
The Helm of Comprehending Languages states:
While wearing this helm, you can use an action to cast the comprehend languages spell from it at will.
The comprehend languages spell in turn states:
For the duration, you understand the literal meaning of any spoken language that you hear. You also understand any ...
The problem with that is that animals have to have an intelligence of 1 or 2:
Intelligence score of 1 or 2 (no creature with an Intelligence score
of 3 or higher can be an animal).
To speak, you need an intelligence of 3:
If you have a penalty, you can still read and speak your racial
languages unless your Intelligence is lower than 3.
So if you ...
But its AC, attack rolls and damage scale with the ranger's proficiency bonus, and its HPs with ranger's level.
Choose a beast that is no larger than Medium and that has a challenge rating of 1/4 or lower (appendix D presents statistics for the hawk, mastiff, and panther as examples). Add your proficiency bonus to the beast’s AC, attack ...