Dejected by doom

As an additional cost to cast this card, sacrifice a creature. Put a number of Doom Counters on
target creature equal to the sacrificed creature's
mana value.
At the end of your turn, replace a Doom counter
from the target creature with a -1/-1 counter.
When target creature goes to the graveyard, target
a new creature and put a number of Doom
Counters on it equal to the mana value of the previous target creature.