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
Allowing your lands to also tap for blue helps with mana-fixing in multicolor decks
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)
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This is because it has one devastating attack which it can use once per turn if you play your cards right
Maybe it builds-up to a limit break-style ultimate ability on some creatures