Berserker Fury, cannot stack with Fury.

Does 2 blade of despair stack?

2 of the same Unique passive will not stack, as stated in game. Stat boosts will stack.

What does berserker's fury do?

Berserker's Fury is a relic power that players can harness at the mysterious monolith. Once harnessed, players will deal up to +5.5% damage with all styles the lower the player's current lifepoints are beneath their maximum level.