Delirium — This creature can't attack or block unless there are four or more card types among cards in your graveyard.
At the beginning of your upkeep, you may mill a card. (You may put the top card of your library into your graveyard.)
Once Patchwork Beastie is attacking or blocking, reducing the number of card types among cards in your graveyard won't remove Patchwork Beastie from combat.