Who is this demanding God
Who rewards our unrealistic sacrifice?
Shall I conform to him,
Or shall I be forever weaker?

Hint 1 - Line 1 doesn't really have any meaning in the answer, it's only there to link to line 2
Hint 2 - the answer is not the God. Also, an important word is "rewards", however the answer is also not the reward
Hint 3 - the answer is the method of sacrifice 
Hint 4 - it is something done in battle