Fissure Fiends are hostile mobs that dwell in Lava. They have penguin-like bodies and feet, with orange skin and a single stalked eye instead of a bird head.
On land, these monsters slide at the player on their stomachs like penguins to attack. They can be found in lava, and they are immune to fire and lava damage. In lava and water, they simply ram into the player as an attack, dealing very little knockback damage in the process compared to on land.
If killed, Fissure Fiends mostly just drop EXP - Rarely, however, they will drop Magma Cream.