Fireforce is a perk in Tower of Guns. It requires the Foundry to be beat before it is unlocked.
"Immune to Env Dmg (Lava/Spike/Etc)"
This perk allows one to wade through lava, sit on spikes, and many other things without taking damage. Those of you that are more adventurous around these hazards will like this perk; you'll take less damage scrounging for secrets in dangerous spots.