Bloodlust is a unique spell effect, but an insignificant one. While bloodlust increases attack briefly, iron skin increases defence.

The spell ingredient bloodstone can produce the spells:

vampire,

bloodlust and

subversion.

All three spells here are offensive. Bloodlust is rarely used. It can produce the ultimate strength army for a moment, but it requires a lot of housekeeping due to requiring many shots (being a of a timed duration). A vampire is a very cheap troop, extremely versatile and an excellent morph target. However, subversion is the spell of choice here. Even when things seem hopeless, you can subvert a creature which suits your tactics, or already has good tactical positioning, and get back into the game. Subversion is one the most enemy-annoying moves available - neither vampire nor bloodlust can reproduce the same level of howling from your human opponent...