Give Silverclad Ferocidons indestructible, if needed, then deal any amount of damage to it.
Silverclad Ferocidons triggers, causing each opponent to sacrifice a permanent.
Mayhem Devil triggers for each permanent sacrificed this way.
Resolve the first trigger, dealing 1 damage to Silverclad Ferocidons.
Repeat from step 2 until no opponent controls a permanent.
Resolve all remaining Mayhem Devil triggers, dealing that much damage divided as you choose among any number of targets.

Each opponent sacrifices all permanents they control

Near-infinite damage

Silverclad Ferocidons

Mayhem Devil

Give Silverclad Ferocidons indestructible by any method.
Deal damage to Silverclad Ferocidons, with all but 1 of that damage being prevented by Temple Altisaur.
Silverclad Ferocidons, Ghyrson Starn, and Spark Double trigger.
Resolve the Spark Double trigger, dealing 2 damage to any target.
Resolve the Ghyrson Starn trigger, dealing 2 damage to Silverclad Ferocidons, with all but 1 of that damage being prevented by Temple Altisaur.
Spark Double and Silverclad Ferocidons trigger.
Resolve the Silverclad Ferocidons trigger, causing each opponent to sacrifice a permanent.
Resolve the Spark Double trigger, dealing 2 damage to Silverclad Ferocidons, with all but 1 of that damage being prevented by Temple Altisaur.
Ghyrson Starn and Silverclad Ferocidons trigger.
Repeat from step 5.

Combos with "Silverclad Ferocidons"