Unless you Fusion Summon this card, you can't use its last effect, turning it into just a big beater. And who the heck wants to use the last effect anyway, after all the trouble to summon this thing? The last effect removes it from the field.....
Which means a huge beater is all people gonna use this card for. And it's nice to see Konami still hasn't learn that hard to summon big beaters like this one needs to be worth it to summon -_-
This thing is a huge sitting duck against various card effect.....
Also, you would use this card's effect during your turn, not opponent's turn.
The perfect play with this thing is to let a CB gets destroyed in battle during opp's turn, activate "Ultimate Crystal Magic" to Fusion Summon this thing, then on your next turn, nuke the field and summon the basic Rainbow Dragon, now that you have 7 different CB in the graveyard. Then OTK the opponent.