Sealed Vanguard Series 3 booster comes with 8 cards: Eladamri, Oracle, Lyna, Sliver Queen, Brood Mother, Takara, Multani, Sidar Kondo
Her champion, Callaphe, Beloved of the Sea, protects your creatures and enchantments from removal by increasing the cost of spells that target them
So when two Near Mint copies sold on May 7th (breaking a four-month stretch of no sales), those few data points were enough to spike the cards Market Price
It is also the Creature in Magic: The Gathering with the highest possible power on its own, without infinite combos, which is nothing to scoff at for a game that has been around for over 30 years
Lorcana Azurite Sea card list & price guide
I'll number them with my actual number in the set