Allowing your lands to also tap for blue helps with mana-fixing in multicolor decks
As always, card prices may fluctuate and are subject to change
This means that it can cast a spell which destroys all the cards in the battlefield in one go, both opponents and their own, levelling the field in a completely fair manner
I dont know what exactly these were, but it appears from the little information I have that there were a couple of European publishers, who released some kind of preconstructed decks and this was in those decks
This is because it has one devastating attack which it can use once per turn if you play your cards right
If the regeneration shield is used, Skithiryx isn't destroyed, all damage marked on Skithiryx is healed, it becomes tapped, and it's removed from combat (if applicable)