Cavalier of Night | Glasspool Mimic // Glasspool Shore | Ashnod's Altar

Cards

All permanents on the battlefield (
Glasspool Mimic // Glasspool Shore as a copy of
Cavalier of Night).

Activate
Ashnod's Altar by sacrificing
Glasspool Mimic, adding ({C} magic symbol) ({C} magic symbol) .
When
Glasspool Mimic dies, its second ability triggers, returning itself to the battlefield as a copy of
Cavalier of Night.
When
Glasspool Mimic enters the battlefield, its first ability triggers, choose not to sacrifice a creature.
Repeat.