For those that don't know yet, the upcoming legendary event will apparently be a fusion event for Mother Cybele .  She's a knight rev, support force champion, and her kit is:

Mask of Dread [ATK]
Attacks all enemies. Has a 25% chance of placing a 30% [Decrease SPD] debuff for 2 turns. Also fills this Champion’s Turn Meter by 15%.

Soul Shepherd (Cooldown: 6 turns)
Places a [Revive On Death] buff and a 60% [Increase DEF] buff on all allies for 2 turns. 

Uncanny Transfer (Cooldown: 6 turns)
Swaps HP with an ally. If this Champion’s HP is equal to or higher than the target’s HP after the swap, fills this Champion’s Turn Meter by 40%, places a 30% [Increase SPD] buff on this Champion for 2 turns, and places a [Block Damage] buff on the target ally for 1 turn. If this Champion’s HP is lower than the target’s HP after the swap, fills the target’s Turn Meter by 40%, places a 30% [Increase SPD] buff on them for 2 turns, and places a [Block Damage] buff on this Champion for 1 turn. Also places to 15% [Continuous Heal] buffs on this Champion for 2 turns.

Gravewalker [Passive]
Fully heals the ally with the lowest HP whenever this Champion is killed. Heals all allies by 20% of their MAX HP and fills their Turn Meters by 15% whenever this Champion is revived. 

To be honest, I'm not seeing it.  This doesn't feel like a great champion to me, especially for a fusion event which is usually more difficult than a fragment one, as you have to level and ascend up so many champions just to get it.

The Gravewalker passive is very situational and requires her to be revived, which means timing the A2 correctly (which is on a 6 turn cooldown, hopefully booked down to 4?  still slow).  It also means that you will probably prioritize the A2 for when she is close to dying instead of when your allies are.  If it's anything like Ursula's, then the AI will just use it anyway even if someone isn't dead because of the 60% increase defense buff.

The A3 also feels odd and situational.  Warcaster (an epic champion) can place block damage on everyone for 1 turn for the same base cooldown, and even that is situational.

Maybe others have better thoughts?  Currently thinking I'll skip this one