Ratadrabik of Urborg | Leyline of Singularity | Glasspool Mimic // Glasspool Shore

Cards

Cast
Glasspool Mimic by paying its mana cost. Choose to have it enter as a copy of
Ratadrabik.
Put
Glasspool Mimic into your graveyard due to the legend rule.
When
Glasspool Mimic dies,
Ratadrabik triggers, creating a token copy of
Glasspool Mimic that is a copy of
Ratadrabik but is a 2/2 Zombie in addition to its other types.
Repeat from step 2 using the
Glasspool Mimic token instead.

This combo produces a mandatory infinite loop that'll cause the game to end in a draw if it isn't interacted with.

This combo has been estimated to be Spicy (Bracket 3-4+).