If you control no cards: Send 1 "Lady of the Lake" from your Deck to the Graveyard; Special Summon 1 "Merlin" from your Deck and if you do, add one "Morgan, the Enchantress of Avalon" from your Deck to your Hand. You can only activate one "Call of Camelot" per turn, also you cannot special summon from the extra deck for the rest of this turn except for "Noble Knight" monsters.
Massive recovery/combo starter for Noble Knights. It's an instant Morgan if you use Merlin to summon a level 5 and then summon the level 5 Synchro with lady. On the other hand it doesn't let the deck use Summon Sorc which hurts consistency.
While a +1 with a lot of potential, the card does have a weakness in its Garnet problem. Lady in the Lake is a one of, at best in the deck. This card is both Xenophobic and locks your Merlin/Morgan plays by the # of Lady you play.