Fireman's Boots

The Fireman& is a item in Risk of Rain that leaves a fire trail behind the player when walking.

Character Synergies
The Acrid and his poison trail work wonderful with this, simply adding even more DoT damage to it.(need confirmation, i saw only 1 dot poping up, from fire also cut the slow effect from caustic sludge).

Item Synergies
Having more movement speed items (Paul's Goat Hoof, Red Whip, etc.) will cause a longer trail.

Trivia

 * The fire trail of Fireman's Boots and Burning Witness do not stack with each other. Only one fire trail is made. It is not confirmed which item works.

Achievement
This item is unlocked by standing in lava for 1 minute straight. Despite common beliefs, because lava deals damage based on a percentage of your maximum health, the best way to do it is not to stack up on HP items. Rather, if you're looking to get the achievement quickly, the best thing to do is to play with the Command and Glass artifacts on, and get as many Guardian's Hearts as possible. This will keep your maximum health low, while boosting your actual health, allowing you to easily stand in the lava, taking only 5-10 damage per tick.