I rather like this idea, although I'm not sure the stats are sufficient enough for what appears to be an end-game item. Maybe something like this?
VOLCANIC EMBRACE
Build Path: Bami's Cinder + Glacial Shroud
+400 health
+35 Armor
+10% Cooldown Reduction
+300 Mana
Unique Passive -- Immolate: Deals 6 - 23 (based on level) magic damage per second to nearby enemies. Deals 50% bonus damage to minions and monsters (400 range).
Unique Active -- Solidify: Snare yourself and all enemies within 400 range for 0.5 - 1.5 seconds (based on level). 60 second cooldown.
It's half weaker Sunfire, part Randuin's, and part Frozen Heart. It's also kind of fun to combine Bami's Cinder and Glacial Shroud to make something that freezes lava around you to snare people caught in it.