Living Lava Titan! What's not to love here? I like the concept. It's clean, simple, and it obviously attuned to Fire.

To quote Curtis:

Eruptions are feared, not just because of their devastation, but because they might be a precursor to the magma beast, Magmat. It is a gigantic ooze of living lava that sometimes emerges from volcanoes or the sea of lava in the plane of fire. Magmat's body produces superheated volcanic smoke that covers the battlefield, weakening those that are unfortunate enough to inhale it. Its attacks cover enemies in magma, slowing them and making attacking and the precise movements of magic difficult. Those that are in its way can be pulled into its body, where the magma acts to corrode them.