Delta

An SR Defender Burst 2 who can draw threat with Remember MeB's Decoy and taunt, but she is rarely a core pick.
Recollection1 raises her max HP with each Full Charge, and Last Memory2 grants DEF with each Burst.

Build Recollection1 max HP with Full Charges, apply Last Memory2 DEF on Burst, then open a Decoy and taunt all enemies with Remember MeB.

As a Sniper Rifle she contributes little Burst Gauge, and her Burst cooldown is 40 seconds.

Time Full Charges to refresh Recollection1's max HP.
In phases that need taunt/Decoy, time Remember MeB manually.
Otherwise auto is fine.

There is almost no evidence of pairings tied to recent Raid or Arena main squads. She is only occasionally mentioned as an early SR taunt substitute.

For Decoy/taunt survival, go Vigor Cube, Tempering Cube, then Endurance Cube.

Skip DPS lines such as Elemental Advantage damage and Charge Damage. For taunt/Decoy durability, prioritize 4 lines of Increased DEF, and put Charge Speed in leftover lines to sustain Full Charge.

If you do not plan to use her, leave her at 1/1/1. When leveling, balance Remember MeB's Decoy HP and Last Memory2's DEF, and reinforce Recollection1 only when you need survival.

Not a main pick for Solo Raid or regular bosses. Only occasionally slotted as an SR substitute when you lack SSR taunt/defense.

Remember MeB opens a Decoy and taunts all enemies.
Recollection1 raises her own max HP with each Full Charge.
Last Memory2 raises DEF with each Burst.

Her SR stats and damage are low, making her hard to use as an early main defender.
Her Burst is 40 seconds while taunt/Decoy last 10 seconds, leaving a long gap.
Outclassed by SRs like N102 and Anis.

Delta: Ninja Thief is a Water Code Machine Gun Defender with different skills and a different role. Do not confuse her with the original Delta.