Arcan, Thunder Incarnated

Flash, Flying, First strike
When Arcan enters the battlefield, reveal
any number of instants and sorcery from
your hand. Put a +1/+1 counter on Arcan
for each card revealed in this way.
The first instant and sorcery you cast each
turn costs X less to cast where X is the number
of +1/+1 counters on Arcan.