Wight of the Reliquary does not have summoning sickness.
You control at least one additional creature.
Steps
Activate Wight of the Reliquary by tapping it and sacrificing another creature, causing you to search your library for a land card and put it onto the battlefield tapped.
When the land enters the battlefield, Retreat to Emeria and Retreat to Coralhelm trigger.
Resolve the Retreat to Emeria trigger, creating a 1/1 Kor Ally creature token.
Resolve the Retreat to Coralhelm trigger, untapping Wight of the Reliquary.
Repeat.
Results
Near-infinite landfall triggers.
Put all land cards from your library onto the battlefield tapped.