Zuko, Banished Prince

When you cast Zuko, Banished Prince you may
discard a card. If you do, this spell costs {2} less
to cast.
Zuko, Banished Prince can't be blocked except
by X or more creatures, where X is the number
of -1/-0 counters on Zuko.
{b/r}{t}: Put a -1/-0 counter on Zuko
{0}: Remove a -1/-0 counter from Zuko