Enchantment

, Discard a card: Create a 0/3 blue Crab creature token.
Delirium — Crabs you control get +1/+1 as long as there are four or more card types among cards in your graveyard.
Discarding a card is part of the cost of Scuttletide's first ability. There is no time for players to respond to the ability before the discarded card is in the graveyard.