Zardnaar
Legend
Some thoughts on Baylan's personal quest:
Objective: He want's to end the cycle of jedi-sith-jedi-sith victories.
Means 1) He wants a grey-side victory. So he is looking for the Bindu (voiced by Tom Baker in animation), the incarnation of the grey side. This is interesting because the Bindu has a bone to pick with Thrawn, and hence could be the wild card that is needed to defeat him.
Means 2) He wants to destroy the Force all together. This would made him a version of Kreia (KotOR2). It might be significant that Darth Sion was also a character from KotOR2. If he is partially successful, managing to damage the Force, it would explain "The Force Awakens" (I didn't know it had been asleep).
KoToR2 theory is kinda doing the rounds along with the being calling to him is based off Abeloth aka the mother of those force gods father, son, daughter.
Coukd also be something new or based on another entity borrowed from Legends.