The mountain drake gives additional damage against epic monsters and turrets.
"Earthen Arms" grants 10/20/30% additional damage (based on stacks; +50% if they have Mark of the Elder Dragon) as true damage to epic monsters and turrets.
Does this damage apply to minion damage? I'm presuming that it does not as they do not carry the buff.
What about Zz'Rott portals? Do the spawned minions do additional damage to turrets?