Vidar, God of Silence

This spell cost {1} less to cast for each creature your opponents control with a counter on them.
Wither, First Strike, Evolve
Whenever Vidar, God of Silence attacks, put a +1/+1 counter on Vidar, God of Silence.
Remove a +1/+1 counter from Vidar, God of Silence, put a -1/-1 counter on target creature, then draw a card.