Osier, Magiteer of the Waves

When this card deals combat damage you may:
(1) reduce that combat damage by the cmc of up to one Instant or Sorcery you select, cast for free, then exile from the damaged player's graveyard. Combat damage cannot be less than 0. THEN
(2) After step 1 resolves: take control of a number of artifact tokens from damaged player where the sum of the tokens' cmc is equal to or less than twice the recalculated damage dealt.
Trample, Changeling