You can Special Summon this card (from your hand) by revealing 1 Level 7 or higher monster from your hand. You can only Special Summon "Angel O1" once per turn this way. While you control this Special Summoned card, you can Tribute Summon 1 Level 7 or higher monster in Attack Position during your Main Phase, in addition to your Normal Summon/Set. (You can only gain this effect once per turn.)