Physical 
Reverb elements, who belongs to the COLUMBA faction. Their position in combat is Mid.
Livia is an extremely versatile character whose playstyle changes depending on the kind of team she's placed in. She has great cycling for herself, with her first card, [Impact Sword], automatically drawing her second card, [Spirit Nocturne]. This second card is rather unique as it will change drastically in effect depending on the color of the card that was used before it is played:
Red makes Red cards deal 30% more DMG and stacks, making it a fantastic buff for long fights.
Blue grants a Shield to a target of choice.
Yellow draws cards and synergizes with [Electrify] teams
Green heals.
Purple inflicts two debuffs on enemies, [Moemoe] and [Confuse].
Similarly, her Ultimate uses the same mechanic, with similar effects. The main difference here is that Blue can inflict [Chill] and buff Livia's DEF, and Purple can generate a special card, [Strange Spark].
[Strange Spark] is an extremely powerful Ultimate that can be used up to three times in a row, completely ignores Target's DEF and gains extra multiplicative DMG based on the amount of cards in the Discard pile.
Playstyle and Key Mechanics
Livia has a unique mechanic called [Consonance]. Her cards change color based on the color of the previous card used by the team, and consequently change Livia’s playstyle and role in the team as well. The downside of this is that it can be quite tricky to use exactly the effect you want in the precise moment you want, especially if you’re using Auto-Battle.
Red Cards: Red focuses on direct DPS. It also brings [Interrupt] (self-explanatory) and [Break] effects, with the latter being capable of removing Shields, Barriers, Force-Fields and Block.
Blue Cards: Blue revolves around DEF, being capable of placing shields on allies, buffing Livia’s own DEF, and triggering [Chill] on enemies with [Finale Waltz]. This side is more useful when paired with Ice tanks like Akira, Wensheng and Tennie.
Yellow Cards: The Yellow version of Livia’s cards all bring [Electrify] effect, being suitable for that kind of team, especially when using Yellow cycling cards such as the ones from Arcana, Stella and Fenia.
Green Cards: The Healing cards. The lowest damage cards from Livia, and their healing can only function as a complement for battles when a lot of healing is needed, since you will already need to bring a proper healer to trigger these cards anyway.
Purple Cards: A mix of Damage and Utility, Purple can inflict debuffs such as [Moemoe] and [Confuse], as well as drawing [Strange Spark]. This side of Livia is only unlocked after reaching Resonance 5, and despite being the one with the highest damage potential, it’s also the trickiest to use.
Investment
Awakening 1 - This Awakening is more impactful for Red teams. It draws a [Impact Sword] at the start of battle, this being the only one of Livia’s cards that doesn’t have the [Consonance] mechanic.
Awakening 2 - A last-ditch effort, when Livia is defeated in battle, triggers [Invincible] and [Finale’s Waltz: Red]. Not very useful overall, since a character in Livia’s position shouldn’t be dying anyway, but can help in a clutch moment.
Awakening 4 - Arguably Livia’s best Awakening, and one of the reasons to prioritize her in Purple builds for the late game. Every time [Strange Spark] is used, all allies’ ATK and DEF increase by 1%, up to 20%.
Awakening 5 - Enables Livia’s use in Reverengy teams. Whenever a Black card is destroyed, Livia heals the ally with the lowest HP.
Resonance
Resonance 1 — Enables Livia’s use in [Electro] teams.
Resonance 2 — Gains 2 more Cost at the start of the battle, an overall useful trait for any team.
Resonance 4 — Spirit Nocturne is Livia’s main Card. By reducing its cost by 1, she becomes significantly stronger and more useful as her cards can be spammed more easily.
Resonance 5 — Enables Livia’s use in Purple teams.
Synergies
❗ ❗ ❗ The Synergies mentioned here are merely samples. Taking their core mechanics as an example, you can use many other characters as replacements or other synergies. ❗ ❗ ❗
Verlaine: Verlaine is another adaptable, multi-purpose character. She’s a sub-DPS, much like Livia, and they can support each other in perfect synergy.
Margiela: One of the few other characters who have access to [Strange Spark], by having this card appear more often, it also speeds up the buff stacks from Livia’s Awakening 4.
Fenia: Fenia’s [Bag of Tricks] becomes twice as useful when paired with Livia, since it will trigger her Yellow cards, thus creating a harmonious match. Furthermore, Fenia is often used in [Reverengy] teams, and if you have Livia at A5, she’ll be able to help with survivability there.
Gear and Affixes
Some examples of overall good equipment choices for Livia. For specific picks, please check the respective teams.
Weapons:
UR Exile Code: Using [Leader Skill] enables the next Purple card to deal 50% more damage. (Great to combo with [Strange Spark])
SSR Radiance Chaser: [Strange Spark] deals 20% more damage. This effect stacks.
SSR Nightfall Starquest: Playing a Purple card has a 10% chance to generate a [Nova] in your hand. The trigger rate stacks. (Specific for Margiela teams)
SR Viscera Collector MK 0: Using [Leader Skill] restores 0.4 Cost. This effect stacks. (General Support/Sub-DPS use)
R Enchanted Sword: Playing a Purple card has a 10% chance to draw a card. The trigger rate stacks. (For Purple teams, if you feel that your Draw is too slow)
R Magic Wand: Playing a Purple card has a 20% chance to restore 1 Cost. The trigger rate stacks. (For Purple teams, if you feel want to increase cost recovery and don’t have Viscera Collector MK 0)
Armor:
SSR Simulated Stars: Using [Leader Skill] restores 5% HP. This effect stacks. (For general use).
SSR Garden Guardian: Restores 0.5% of HP every second. (If you don’t have Simulated Stars).
Accessory:
UR Hulton Balloon: Draws a card after playing a 3-cost or higher Yellow card. (If using Livia in an Electrify team).
SSR Mobius: Cards in your hand are replenished 0.25 seconds faster. This effect stacks. (For general use).
SR Magic Spring: Restores 0.02 Cost per second. This effect stacks. (If you feel you need more Cost recovery or if you don’t have Mobius).
Affixes:
Using [Leader Skill] restores 0.2/0.3 Cost. This effect stacks.
Using [Leader Skill] restores 2/3% of own Max HP. This effect stacks.
Using [Leader Skill] increases own ATK by 0.5/1%. This effect stacks.
Restores 0.01/0.02 Cost per second. This effect stacks.
Increases own ATK by 1/3%. This effect stacks.
Increases own ATK by 10/30. This effect stacks.
Playing a Red card increases own ATK by 0.2/0.5%. This effect stacks.
Increases final DMG dealt by 2/5%. This effect stacks.
Using [Strange Spark] increases wearer's ATK by 0.5/1%. This effect stacks.
[Strange Spark] deals 5/10% more damage. This effect stacks.
Playing a Purple card restores 1/1.5% HP. This effect stacks.
Cards are replenished 0.1 seconds faster. This effect stacks.
