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.

NOTE: Stock image, not actual card.