You control a permanent that can tap to produce at least ({U} magic symbol) .
Steps
Activate Carrion Feeder by sacrificing Coral Trickster.
When Coral Trickster dies, Missy's first ability triggers, returning Coral Trickster from your graveyard to the battlefield face down as a 2/2 Cyberman artifact creature.
Resolve the Carrion Feeder ability, putting a +1/+1 counter on it.
Activate a mana-producing permanent by tapping it, adding at least ({U} magic symbol) .
Activate Coral Trickster's morph ability by paying ({U} magic symbol) , turning it face up.