Malicious Insider

Flying, trample
Whenever an opponent casts a spell, put a +1/+1 counter on Malicious Insider.
Workload 4 - At the beginning of your end step,
if Malicious Insider has 4 or more +1/+1
counters on it, remove all +1/+1 counters from
it. If you do, for each counter removed this way,
put the top 5 cards of your library into your
graveyard.