Tier 1: Raise Militia (S, loses population, gains a basic unit), Backlash (T, direct damage to a summon)
Tier 2: Gargoyles, Hell Hounds
Tier 3: Fire Elemental
Tier 4: Fire Giant
Tier 5: Nightmares
Tier 6: Efreet
Tier 7: Chaos Spawn
Tier 8: Fire Drake