Firekin

Firekin are level 85 creatures that appear from fire portals to guard from wisps in the Molten Front, during the quest Wisp Away.

They look like red grells and will initially try to kill the wisps by casting fireballs on them, until they're killed or change aggro towards something else. They spawn rapidly, but are easily killed due to their low health. Only 8 firekin (which have to be killed) will spawn each time you do the quest.

Speculation
Much like Flame Imps, they may be flamekin.