Do keep in mind however, that you cannot Summon from the Extra Deck as long as they remain on your field
SR Super Rare Centur-Ion Gargoyle II X DARK Level 8 [ DragonEffect ] ATK 2000 DEF 3000 You can send 1 face-up "Centur-Ion" card you control to the GY
If the opponent's monster is in Defense Position and has fewer DEF than the attacking monster's ATK, it is destroyed, and its owner takes no battle damage, unless the attacking monster is able to inflict "piercing" battle damage
The only downside to this amazing retrain is that it is only available in one set and in the highest rarity
In Magic, there are Waterbreathing creatures (that use mana to gain +x/+0), and White has the odd one kicking around (I think every colour does ultimately), you could throw something like that on
So if you change 'Summoned Skull' to Level 3, and Summon it, it can attack even if 'Gravity Bind' is active