Karthus, Mage Ascendant

Instant and sorcery spells cost {2} less to cast.
Whenever a spell you control counters a spell Karthus, Mage Ascendant deals damage equal
to the countered spells converted mana cost to
that spells controller.
Whenever an instant or sorcery you control is countered return that spell to your hand.
This power is but a drop in the ocean.