Curse of the Swamp

Enchant player
At the beginning of enchanted player's upkeep,
that player chooses a non-swap land and a
non-token creature. The land loses all abilities
and types and becomes a swamp. The creature
loses all abilities and becomes a black spirit with
base power and toughness 1/1.

"Don't listen to the guards! The curse is spreading!
Don't list-" — "Mad man" Manx