Legendary Planeswalker — Grist
As long as Grist, the Hunger Tide isn't on the battlefield, it's a 1/1 Insect creature in addition to its other types.
+1 : Create a 1/1 black and green Insect creature token, then mill a card. If an Insect card was milled this way, put a loyalty counter on Grist and repeat this process.
−2 : You may sacrifice a creature. When you do, destroy target creature or planeswalker.
−5 : Each opponent loses life equal to the number of creature cards in your graveyard.
Grist's second loyalty ability doesn't require a target. If you choose to sacrifice a creature as it resolves, the reflexive triggered ability triggers and you'll choose a target creature or planeswalker to destroy. This will happen even if Grist isn't on the battlefield when the loyalty ability resolves.