Cast Phantasmal Image by paying ({1} magic symbol) ({U} magic symbol) , having it enter the battlefield as a copy of Gyruda.
Put Phantasmal Image into your graveyard due to the legend rule.
Mortuary triggers, putting Phantasmal Image on top of your library from your graveyard.
Phantasmal Image's enter the battlefield ability triggers, causing each player to mill four cards and you to return Phantasmal Image from your graveyard to the battlefield as a copy of Gyruda.