Fel Stamina was a talent in the Demonology tree, you would need to spend 13 points in Demonology to max it.
Rank table[]
Rank
+% Stamina
+% Health
1
1%
2%
2
2%
4%
3
3%
6%
Notes[]
4-5 ranks can mean 1-2 more hits required to kill your Voidwalker up until the end-game instances. When combined with 3 ranks of Improved Voidwalker it actually makes him an excellent soloing tank so long as you don't spam shadowbolts from the outset of the fight.
5 ranks will make a serious difference in the staying power for your Felhunter when you're fighting higher-level caster mobs because more HP means it will take them more spells to kill him, which in turn gives them more chances to re-cast their defensive spells which Felhunters love to devour.
The Succubus and Imp won't get as much out of this talent as the other two. They benefit more from [Fel Intellect] than Fel Stamina.
[Fel Intellect] than Fel Stamina.
Hotfix (2009-01-07): Now properly removed. 
