Oboro from your hand onto the battlefield, and then repeat this process once if you control eight or more lands, putting any other land from your hand onto the battlefield instead.
When
Oboro enters the battlefield,
Bloodghast and
Retreat to Coralhelm trigger.
In response, activate
Oboro's first ability by tapping it, adding ({U} magic symbol) .
Activate
Oboro's second ability by paying ({1} magic symbol) , returning it from the battlefield to your hand.
Resolve the
Bloodghast trigger, returning it from your graveyard to the battlefield.
Resolve the
Retreat to Coralhelm trigger, untapping
Zimone and Dina.
Repeat.
Results
Infinite card draw.
Infinite draw triggers.
Near-infinite ETB.
Near-infinite LTB.
Near-infinite death triggers.
Near-infinite landfall triggers.
Near-infinite sacrifice triggers.
Put all lands from your hand and library onto the battlefield.