Arcana

An Electric Burst 2 Supporter Rocket Launcher whose support contribution is large in teams sequenced with an Electric Burst 3 Nikke in the same Full Burst, but tricky to slot as a general-purpose supporter.
She must keep the Wheel of Fortune card until Full Burst ends, and an Electric Burst 3 Nikke must have used Burst in the same cycle, for Awakened Destiny1 and Cycle of Destiny2's big cooldown and attack buffs to trigger.
Against Water Raids and bosses (Electric has the advantage), elements line up, giving her high value in Solo Raid and boss teams.

Her Burst Shackles of DestinyB gives all Electric allies the Wheel of Fortune card to raise attack damage, and hits all enemies with Burst Skill damage and the Judgement card to raise their damage taken.

When Full Burst Time ends, if she still has the Wheel of Fortune card, Awakened Destiny1 gives the Electric ally with base Burst stage 3 who just used a Burst Skill the Magician card, greatly reducing S2 cooldown and raising attack damage. At the same time, it grants all allies Increased ATK based on caster's ATK.

Cycle of Destiny2, if the Wheel of Fortune card remains when Full Burst ends, gives the Electric B3 ally who just used Burst the Strength card to raise ATK based on caster's ATK, and under the same condition gives all allies the Death card to reduce Burst Skill cooldown and briefly grant Increased ATK. Also, each time Full Burst ends, it unconditionally grants all allies increased attack damage.

Arrange the team order so Full Burst ends naturally after an Electric B3 Nikke uses Burst in the same Full Burst cycle.
Manage range and survival so the Wheel of Fortune card from Shackles of DestinyB does not drop before Full Burst ends.
Land your shots during Rocket Launcher reload windows.

Rocket Launcher reloads are long, so easing reload comes first. Raise Max Ammo to reload less often, and choose ammo-refill cubes by situation. If Harmony Cube levels differ a lot, use the higher-level cube before following the ranking.

Elemental Advantage damage and ATK are the baseline. Max Ammo lines help keep reloads from disrupting buff timing.

Her buffs come from Awakened Destiny1 and Cycle of Destiny2, so raise S1 and S2 first. Shackles of DestinyB mainly opens the conditions, so it can be raised later.

Her elemental edge is clear when placed in the Burst 2 slot against Water bosses (Electric has the advantage) and in Electric Solo Raid. She is hard to fit in general story or Arena teams.

When conditions are met, she can give an Electric Burst 3 Nikke attack damage, caster's ATK, and cooldown reduction support all at once within the same Full Burst.
Each time Full Burst ends, all allies get increased attack damage, and meeting the condition also adds Increased ATK based on caster's ATK.

If Wheel of Fortune card upkeep and Electric B3 alignment slip, her key buffs drop out. She has almost no survival utility like healing or shields.
With a 40-second Burst cooldown, the team needs another Burst 2.