Cavalier of Night | Glasspool Mimic // Glasspool Shore | Yahenni, Undying Partisan

Cards

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

Activate
Yahenni, Undying Partisan by sacrificing
Glasspool Mimic.
When
Glasspool Mimic dies, its last ability from
Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of
Cavalier of Night.
When
Glasspool Mimic enters the battlefield, its first triggered ability from
Cavalier of Night triggers; choose not to sacrifice a creature.
Resolve the
Yahenni, Undying Partisan ability from step 1.
Repeat.