Level vs Hit Dice for PCs

I’m trying to think of what game mechanics hinge on the hit dice (as opposed to level) of PCs. Since ACKS doesn’t let PCs off the hook for charm/sleep/etc., the only one I can think of is cleave (in the RAW, the number of cleave attacks is a function of the characters hit dice). Any others spring to mind?

Most effects hinge on the hit dice of the PCs - Confusion, Death Spell, Sleep. The only spell which can affect a PC despite him being over the hit dice limit is Charm Person.
An 8th level fighter can’t be put to Sleep, for instance, even though humans are 1HD creatures.

Thanks, Alex! Hold Person also affects PCs regardless of HD in v32; I must have assumed Sleep followed suit.

You are correct! It’s Charm and Hold, but not Sleep.

Wow. All those years of gaming, I never ever even have thought of distinguishing between hit dice and level… For me, level was equal to hit dice (or vice versa)
So, if there would be a spell, that would affect a 10 hit dice creature, my level 10 fighter would not be affected because he only has 9 hit dice (levels 1-9) plus 2 fixed hit points (for level 10)?

Beastman, most spells (that I know of) that affect creatures affect “creatures 10HD or less”, for example. So a 10th level fighter (with 9+2HD) would be affected. But if the spell specified that it worked only creatures of EXACTLY 10HD, then the fighter wouldn’t be affected, correct.