Sadistic Elf

Whenever X -0/-1 or -1/-1 counters are put on creatures your opponents control, this creature gets +0/+X until your next end step.
Manaladen 7- infect. (Whenever you cast a spell, put a number of Mana counters on this permanent equal to that spell's mana value. As long as there are 7 or more Mana counters on this permanent, it gains the indicated ability.