Shes not LLM.

'Special Attack' = 'Special' bracket in the dmg formula. Similar effects like Berserk and Vigor. She outright lets your whole party a flat +100% final dmg increase if you meet the requirement.

As for how viable she is, we need more time to test her out. Only one of my friend got her and with my randomly set up 3 Dark 2 Other party, the Dark units dealt sifnificantly higher dmg than when I use Anubis support. The real question is how much can a Null weapon grid can boost this advantage to the point where it can compete face to face with mono 100% teams.