In another Tweet, she states that the Pikachu card will also be released in January, but doesn't reveal how to get it
These, my friend, are adventures
While a 6/6 creature is not all that imposing, Deep Spawn has the ability to make itself untargetable until end of turn for just a single blue mana, effectively has some form of evasion with the Trample ability, and also mills cards from the top of your deck in to your graveyard during your upkeep (which can fuel further reanimation shenanigans on future turns)
Its Cosmic Power ability allowed players to discard two cards to the bottom of their deck and refill their hand up to six cards, making it an excellent draw engine
During their turn, if their opponents Active Pokmon is Knocked out by damage from an attack used by their Tera Pokmon, they take one extra Prize card
However, there was no further documentation of the signature