Source
You can check the original articles for both characters here and here.
New character - Valak

Valak is a Fire Priest who specializes in buffing her allies and keeping them alive. Compared to other Priests, she's more offensively aligned - she can provide her allies with a buff that not only heals allies after they are attacked but also instantly do damage back to the attacker.
In Kalpa, Valak's mirror is considered a staple in Fire teams and in our version it will be the same - considering that the only Fire healer available to us is Future King (R Rarity).
You can watch her showcase here.
New character - Susie & Susan

Susie & Susan are the first Twin-type character added to the game. They're classified as Dark Mage and you already could see them in action in the early story - as they appeared in the Campaign as enemies (initially).
Susie & Susan specialize in debuffing enemies and controlling the battlefield, but they are also very mobile for a Mage as they can teleport. In Kalpa, their mirror today sits among the best characters together with Charlotte and Semi.
You can watch their showcase here.