You can only Special Summon "Magister(s) of Endymion" once per turn. When this card declares an attack: You can place 1 Spell Counter on it. Once per opponent's turn (Quick Effect): You can remove 3 Spell Counters from your field; Special Summon 1 monster from your Deck that you can place a Spell Counter on. If this card in the Monster Zone is destroyed: You can place this card in your Pendulum Zone, then place the same number of Spell Counters on it that it had as a monster.
[Pendulum Effect]
Each time a Spell Card is activated, place 1 Spell Counter on this card when that Spell resolves. You can remove 3 Spell Counters from this card; Special Summon both this card from your Pendulum Zone and 1 face-up monster from your Extra Deck that you can place a Spell Counter on, and if you do, place 1 Spell Counter on each.