A newly developed subaquatic Seal type robot. Its breath can freeze the water around them in an instant, creating obstacles when Sonic needs to look for air bubbles. — Sonic The Hedgehog 4: Episode II Website
Steelion attacks by emitting a freezing pulse from its mouth, freezing a small area in front of itself. The main purpose of this attack is to create an obstacle for the player, cutting off shortcuts or preventing the player from reaching a safer area. If the player is in the vicinity of the pulse when it's performed, it will cause damage to the player.
Steelions tend to perform their attack as soon as the player approaches, making them hard to defeat.