Magmen are enemies in Mother 3. They appear as a volcano with legs and a face, with a Pyrefly emerging from its spout. The Pyrefly indicates one of its attacks: to summon Pyreflies to the fight, which it will do very often.
His battle sound is Battle Sound 1 which falls under Code Numbers 439 for regular attack, 440 for Smaaaash! and 441 for Miss.
It's been speculated that this enemy is a reference to Kirby 64's Magman, a Lava being able to summon flying fire-based enemies, Burnis.