Locusta, the Poisoner

Whenever you lose life, put X -1/-1 counters divided as you choose on among any number of target creatures, where X is the half the amount of life lost, rounded up.
Lasting legacy—When this creature is put into your graveyard from the battlefield, you may exile it. If you do, you get an emblem with "Whenever you lose one or more life, put a -1/-1 counter on target creature."