You don't want to give them a million blockers, but if you're going to Overrun or Baru or Craterhoof, it won't matter
This dilutes S11s concentrated card pool across a 196-card English set, significantly reducing your odds of pulling any specific S11 card
If your opponent tries to snag one of your Sea Serpents from your Graveyard with Monster Reborn or Grandsoil the Elemental Lord , you can use Call of the Atlanteans to Summon it first, rendering your opponents card useless
Unlike the cards in the main set, Through the Ages cards do not become legal in Magic's Standard format (though they still are if the existing card was already legal there, of course), essentially just making them alternate art versions of those cards
If you use this effect, during your next Standby Phase the removed from play monster returns to the field
(Player #1 does these things) Player #2s Raigeki Break resolves: destroy it