For those who got Tsukiko: Rejoice! With today's update came the story section that gives Tulien's new accessory, which means the trial is really, really easy using both of them.

The party I used was:

Maeve: Mag tank, 350% water resist, 40k hp and 6k SPR. Unkillable, she sets up cover barrier ailment resists turn 1 and just spams lb fill for the rest.

Sylvie: Magnus turn 1, turn 2 LB.

Tulien: Mine was EX0, only needs his new accessory (enables a 160% earth imperil 89 DEF break after 3 turns) and Earth Breaker (his own TMR).

Chizuru: Turn 1 plant chains, turn 2 uses katana imperil ATK buff magnus whatever. Used a friend with the same setup.

Tsukiko: Turn 1 earth field fill own LB rod imperil then wait.

On turn 3, Chizurus chain with Tulien (using eye of the dragon) and Tsukiko caps. Then, Maeve uses 3x LB fill and Sylvie uses earth magnus 2x LB fill. This means that on turn 4 you can repeat the 3x LB burst.

My Tsukiko is only EX1 and has 7.8k MAG and not capped on everything. Still, on turn 4 the boss had 15% HP. Then, I just repeated both lb fill with Maeve and Sylvie and finished off turn 5. Easy fight =)