From the Super Mario Wiki
“I'm burnin' up inside!”
Helio is a small fiery orb that appeared during the events of Super Mario RPG: Legend of the Seven Stars. Helio cannot really be considered as a regular enemy, as it only appears during the battle against Czar Dragon, in the Barrel Volcano. The dragon often summons several Helios to help him. Helio's only attack consists in ramming one of its opponents in order to damage him. However, the fiery foe also explodes when it hits someone, causing its own death. Helios are weak against Ice, thus Mallow's Snowy can defeat all of them in a single blow.