BG3 characters so far getting cards are Gale, Lae'zel, Raphael, and there is an Instant called Wyll's reversal.
Mechanics revealed so far are Initiative, Undercity (dungeon) , Adventure, Myriad, Dice Rolling, and hinted by Lae'zel's card Experience Counters and\or Energy, Backgrounds.
Also characters from BG1&2 are in the set, one from Baldur's Gate: Descent into Avernus and weirdly one from Ravenloft, Strahds nursemaid, one is new character, and one is the God Bhaal.
I love Raphael, Fiendish Savior, the best so far. Demons, Tiefling, Devils, and Imps get 1\1 and life link, he has flying, and each turn when a creature card enters the graveyard you get a 1\1 Devil with when it dies deal 1 damage to any target. He has the obviously batched Lord synergies, but also good in sacrifice and mill decks.