Cassandra Mythorn

Whenever and artifact enters the battlefield, put
an experience counter on Cassandra Mythorn.
Each artifact creature gets +X/+0 where X is
equal to the amount of experience counters on Cassandra Mythorn.
Whenever an artifact you control leaves the battlefield, you may remove all experience
counters from Cassandra Mythorn and deal
damage equal the amount of experience counters removed to any creature or planeswalker