The rot reaver: an aberration that licks stuff, kills and reanimates it, then feeds on the resulting zombie's energies. I'm not kidding: that's actually what it does.
The bad first: it's got 10 aberration RHD. That's bad for basically any kind of character. 30 ft. speed is average for a medium creature, 20 ft. climb is outclassed by now. Stats are disappointingly low, with +4 to all physical stats, +6 charisma, +2 wisdom, and -4 intelligence. That's something I'd expect of a monster with half this RHD, maybe less.
The reaver's natural abilities are more interesting than its chassis. Rebuke Undead is a very rare ability on a monster: a pity the 10 HD make being a DMM caster very difficult.
Its centerpiece abilities are Wound Rot (any handaxe melee attack that hits lets the reaver make a follow-up touch attack for 1 point of constitution damage) and Animate Dead (anything dead that was affected by Wound Rot in the past 24 hours can be raised as a zombie as a standard action). The first ability's combat utility is small, but present. The second ability is rather limited by the fact that a rot reaver can't animate more undead than it's got HD, and even with the Rebuke Undead pool that's only one 10 RHD and two 5 RHD zombies at most. (also, zombies just kind of suck in general)
Drain Unlife is a final odd ability. On the one hand, handaxes are bad. On the other hand, being able to directly convert an undead creature's HP into healing has its uses. Then again, undead-related limitless out-of-combat healing is already available at the cost of a level and a feat.
Further abilities that are better than nothing, but not worth mentioning separately are 60 ft. darkvision, immunity to energy drain, and the ability to give handaxes 4x crit damage (rather than their usual 3x) when used.
The rot reaver's interesting abilities sadly do not make it powerful enough to function in an at-level party. Ten lost levels is a lot, the stat boosts gained in return are kind of low, and being able to create a few weak zombies sadly doesn't bring them up to par. -0 LA, but definitely balanced if some of the RHD get removed.
Rot Reaver Necrothane
You say 'vicious, malevolent champions of the rot reaver species', I say '20 rhd, bad, -0 LA'. Seriously: its stats barely increase, it gains zero new abilities, and it somehow doubles its RHD while doing so. -0 LA.