Harran

A Burst 3 Electric Sniper Rifle featuring Virus Transfer damage over time and a full-screen Full Burst hit, but she sees no core use in the current PvE meta.
She rarely appears even in top Solo Raid teams.
Newer DPS outclass her, so her investment priority is low.

Her attacks have a chance to apply Virus Transfer damage over time, and killing an affected enemy spreads it to the two nearest enemies. Each Full Charge boosts Pierce and Critical Rate for one shot, and kills stack ATK. Her Burst deals big damage to all enemies at once.

Firing at Full Charge adds Pierce bonus and crit to one shot.
With many mobs, kill stacks and Virus Transfer propagation spread her damage.
Keep her on auto and turn on manual aim only when you want to hit the core directly.

There is little evidence in the recent meta for pairings that run her in the same squad.

Sniper Rifles fill Burst Gauge slowly, so supplement charging with Quantum Cube, and use Adjutant Cube for charged shots. If survival is lacking, add Endurance Cube. If Harmony Cube levels differ a lot, use the higher-level cube over the ranking.

Prioritize Charge Damage and Charge Speed. Fill Hit Rate with gear and Overload, and fit remaining lines to crit and the like.

She is not a meta core, so she rarely gets full investment. If you must build her, raise Plague Transfer1 and Death ScytheB to 4; Predator2 is low priority.

She rarely appears in top Solo Raid or Union Raid teams. She is only occasionally used in early multi-enemy phases.

Virus Transfer spreads to nearby enemies on kill.
With many mobs, ATK stacks build quickly.
Her Burst lands a big hit on all enemies.

Virus Transfer has a 25% chance, so it is unreliable.
In single-boss phases, stacking and spreading barely happen.
She has no core pick role in the Burst 3 damage slot.