Knight’s 3rd and 4th level are good, but not excellent. The first couple of levels are fairly mediocre, too. On top of that, knight gets absolutely nothing worthwhile after 4th until 20th. Which means you’ll want to multiclass, but then the saving throw DCs on your challenges will suffer badly, and you presumably are already low on Charisma, and if your test of mettle doesn’t work, you’ve given up on the best thing about the class.
If you want to go with knight anyway, you’ll want to be as Charisma-heavy as possible. Unfortunately, many of the best options for doing so are not readily available to you.
Instead, you look like a prime candidate for Saph’s horizon tripper build. It was designed around making lock-down possible with minimal available books (even just Core only! but it also points out useful things you could get as you add other books). Tripping is one of the most effective martial tactics, and the only one relevant to keeping things locked down. Creatures that are immune or heavily resistant to tripping do exist, but they’re not that common. Basically only things with no legs are immune, and things with many legs are resistant, so it’s usually easy enough to tell. The big thing is flight: you can trip creatures flying using wings or other appendages. You cannot trip creatures flying magically without wings, as with the fly spell. But Stand Still provides a decent alternative for these cases.
Highlights are these:
Use a level of barbarian and fighter with three levels of ranger. So long as ranger is a favored class, this avoids multiclass penalties if they’re in play, and human is an ideal race anyway since you’ll want feats.
- If Unearthed Arcana is available (it’s sometimes considered core since it’s on the SRD), giving up the level of fighter for wolf totem barbarian gets you Improved Trip as a bonus feat without prerequisites. Excellent trade: you get slightly more HP, and you get a bonus feat just as you would with fighter, but you get to skip Combat Expertise: that’s like getting two feats.
The horizon walker prestige class has two particularly high points here for you: at 1st level, you can take desert terrain mastery to gain immunity to fatigue (including the fatigue after raging), and at 6th level you can take shifting planar terrain mastery to allow yourself to use dimension door once per 1d4 rounds. Dimension door is not exactly ideal, since it kills the rest of your turn, but the cooldown is short and it’s at-will otherwise. It’s not easy to find mobility that good for a martial character with the books that you have. And though the other options are not quite up to the standards of those two options, they’re plenty good enough to keep taking levels thereafter.
Important feats are Combat Reflexes and Improved Trip. If you cannot be a wolf totem barbarian, that means getting Combat Expertise, which is painful, but doesn’t kill things.
- Follow-up feats include Stand Still and Knock-Down. Stand Still gives you an alternative to tripping for trip-resistant or trip-immune enemies, while Knock-Down gives you improved damage against those you can trip.
Spiked chains are actually optional; you probably have enough books there to not run out of better feats to take. A guisarme works nearly as well and does not cost a feat. On the other hand, exotic weapon master is not a terrible class, so you could definitely use a spiked chain to qualify for it.