Avistar

A Burst 1 Supporter who buffs My Idol's attack at the start and end of Full Burst, while she herself holds out with Max HP and healing.
«My Idol» refers to 'a single ally designated in-game', namely Anis: Star.
So while rarely used, if you do use her, always run her with Anis: Star.
As a Supporter, judge her by her idol buffs and re-entry support rather than raw damage compared to main DPS.

Burst «StargazerB» applies Re-enters Burst Stage 1 to all allies and grants herself lasting StargazerB (Max HP increase based on caster's Max HP).

When Full Burst Time starts, if her HP is above a certain ratio and she is in StargazerB, her current HP decreases. Only while in StargazerB does she grant My Idol lasting Projectile Explosion Damage increase and Attack Damage increase.

When Full Burst Time ends, she grants My Idol Aftershow1 (Increased ATK based on caster's ATK), which is removed when the next Full Burst begins. At the same time, she heals based on Max HP and StargazerB is released.

After activating StargazerB with her Burst, meeting the skill conditions (HP ratio, StargazerB active) during Full Burst grants her idol lasting buffs.
When Full Burst ends, her idol gets Aftershow1, and she heals and releases StargazerB.
If several Burst 1 Nikkes grant Re-enters Burst to allies, effect priority can get mixed up, so check your lineup.

Her buff target is a single ally defined in her skill, so she is grouped into teams built around that synergy.

Machine Guns tend to break their support loop when reload gaps run long, so look at reload and ammo first. If the team is stable, you can add more damage boosts.

For a Machine Gun, balance Max Ammo with Elemental Advantage damage and ATK to make the most of ammo and hit count. Fill remaining lines with Crit.

Since most of her buffs sit on Skill 2 and Burst, raise S2 and Burst first.

If you have no notable support Nikke, she can serve as an assistant to Anis: Star.

She grants Re-entry Stage 1 to all allies and chains explosion damage, Attack Damage, and ATK buffs onto her idol before and after Full Burst. After Full Burst ends, she heals and releases StargazerB to prepare for the next cycle.

Her own weapon is a Machine Gun, which may seem mismatched with her idol DPS's weapon and buffs. Overlapping with Burst 1 Nikkes that grant Re-enters Burst can mess up priority.

'My Idol' is an effect that applies only to Anis: Star (Idol Anis). It is considered similar to Chime's 'My King'.