As the title says. New Treant has the ability to "heal" the towers, so Doom should have ability to "burn" them. Why doom and not some other hero? Because Doom was used to destroy trees with his fire! My suggestion is only:
letters are my suggestion.
Blankets the ground in flames, damaging enemies, towers and healing the Doombringer. Also increases Lucifer's attack and movement speed.
Lasts 20 seconds.
Level 1 - 1 damage/health a second, 10% increased speed.
Level 2 - 2 damage/health a second, 15% increased speed.
Level 3 - 3 damage/health a second, 20% increased speed.
Level 4 - 4 damage/health a second, 30% increased speed.
Cooldown: 10 seconds.
Basicly, at lvl 4 it'll be 80 hp damage to tower over 20 sec.