H 727
I don't actually know anything about Thralls or Kostchtchie, but this inspired me:

Prerequisites: evil, rage, proficiency with warhammer

{table=head]level|fort|ref|will|bab|special
1|2|0|0|1|rage +1/day
2|3|0|0|2|cold be hand
3|3|1|1|3|rage +2 str
4|4|1|1|4|cold be heart
5|4|1|1|5|rage +1/day
6|5|2|2|6|cold be bone
7|5|2|2|7|rage +2 con
8|6|2|2|8|cold be sleep
9|6|3|3|9|rage +1/day
10|7|3|3|10|in the black wind[/table]
HD: d12
Skills: 2+int
Class skills: Climb , Intimidate, Jump, Knowledge (religion), Survival, Swim


rage +1/day: rage once more than you already could

cold be hand: all your melee attacks to an additional 1d6 cold damage, and count as magic and evil for overcoming dr

rage +2 str: when you rage, increase your strength by 2 more than you already would

cold be heart: You may use abilities requiring concentration while raging. Also, you are incapable of genuine love or friendship, making you immune to charm effects.

cold be bone: immunity to cold

cold be sleep: Death begins to seep into your body. Like an undead, you are immune to poison and precision damage.

in the black wind: Gain a breath weapon: 15' cone of cold. Usable 3/hour. Does 5d6 damage. Reflex for half, dc 15+con mod.