Add 1 "Endymion" card from your Deck to your hand, then you can count the number of "Spell Power Mastery" and "Spell Power Grasp" you control and/or have in your GY, and place that many Spell Counters among card(s) you control that you can place a Spell Counter on.
You can only activate 1 "Spell Power Mastery" per turn.