Izmir without their uncap is a very old and not very worthwhile character, with her 5* though she is one of the versatile characters for beginner and mid-level players. She has survivability to herself with S3, but her main draw is her support and how much damage she can do herself.
Strengths
Niflheim500% Water damage to a foe (Damage cap: ~630,000). Gain 1 Icy BladeC.A. DMG and C.A. DMG cap are boosted based on number of Icy Blades (Max: 5 / Can't be removed) Duration: Indefinite and 15% ATK Up (Stackable / Max: 40%)ATK is boosted (Stackable / Can't be removed) Strength: 15% (Max: 40%)Multiplier: Unique StackableDuration: IndefiniteStacking: Single Target. At level 55: Effect enhanced. is a nuke that she can use to build up Icy BladeC.A. DMG and C.A. DMG cap are boosted based on number of Icy Blades (Max: 5 / Can't be removed) , a stack that builds up to greatly increase Charge Attack damage for herself and once high enough she can pass around Dream BladeC.A. DMG and C.A. DMG cap are boosted based on number of Dream Blades (Max: 2 / Can't be removed) to increase C.A. Specs for her allies.
Izmir's skill, FarewellAll allies gain 50% / 50% Critical Hit Rate UpAttacks made with elemental superiority have a chance to deal boosted DMG Strength: 50% chance of dealing 50% more damage.Duration: 3 turns. (Consumes 20% of charge bar.) At level 100: No longer consumes charge bar. All allies also gain KeenSupplemental DMG to critical hits Strength: 1% of foe's max HP (Damage cap: 50,000)Duration: 3 turns and RevitalizeRecover HP each turn. Boost to charge bar if HP is full. Strength: (Healing cap: 500) or 10% charge barDuration: 3 turns. is extremely versatile with the many things it brings to the table.
Izmir is also example of how Extended Mastery Points can turn a good character even better, with her EMP passive she can use FarewellAll allies gain 50% / 50% Critical Hit Rate UpAttacks made with elemental superiority have a chance to deal boosted DMG Strength: 50% chance of dealing 50% more damage.Duration: 3 turns. (Consumes 20% of charge bar.) At level 100: No longer consumes charge bar. All allies also gain KeenSupplemental DMG to critical hits Strength: 1% of foe's max HP (Damage cap: 50,000)Duration: 3 turns and RevitalizeRecover HP each turn. Boost to charge bar if HP is full. Strength: (Healing cap: 500) or 10% charge barDuration: 3 turns. to get more Icy Blade stacks.
She's very strong in the hands of beginners due to the fact that she has Ice QueenAmplifySeraphic modifier damage against Fire foes by 20%. At level 95: Also amplifiesSeraphic modifier other Water allies' damage against Fire foes by 20%. 3% boost to Water allies' critical hit damage cap. which becomes AoE at level 95. As a result she herself can substitute for
Her extremely high yet fluctuating damage is a great strength but as I mentioned, it's inconsistent. She can pass on her great damage with Dream BladeC.A. DMG and C.A. DMG cap are boosted based on number of Dream Blades (Max: 2 / Can't be removed) stacks for her allies.
Weaknesses
As a continuation of her last strength she her damage is inconsistent due to the fact her damage moves with her Icy BladeC.A. DMG and C.A. DMG cap are boosted based on number of Icy Blades (Max: 5 / Can't be removed) stacks, which she does consume after using a Charge Attack at 5 stacks.
She also takes a very long time to reach her maximum potential. She's mostly better suited for longer fights.
Her S3's status, Ice BarrierWhile deployed: DEF, multiattack rate, critical hit rate, and charge bar gain are boosted / Debuff immunity / Hostility is lowered (Can't be removed / Ends when endurance hits 0) is very good but can be very quickly burned through with AoE normal attacks from high level bosses.