The Myth of the Valkyrie's Progressive starts tomorrow August 15th, and you'll have the chance to get Olnir who's featured on Chapter 4 of the time-limited book Weodmonath.
Olnir is a thunder heavy attacker with low cooldown skills who can apply Shock to enemies and Shock Hater to herself and blast everyone! She can also revive an ally, but not for free: She will sacrifice herself. At the beginning of every battle, Olnir will cast an Immunity to Tortures upon her allies.
Here's her official sheet, so you can check her skills best: