TLDR; of Momo or Mo Xiu's abilities. For a little more details, use the other section.

Primary Skill - Ink Form
Recharges [Rhythm] Charges (The bar) to full and spawn 2 orbs that gives 10 [Rhythm] Charges each.
[Rhythm] Charges cap unlocked
Attack uses 15 [Rhythm] Charges
If you do not have enough [Rhythm] passive charge, consume 0.8s of skill duration for every missing charge instead

Reduced Final Dmg taken.
-2s remaining skill duration on lethal instead of dying
[Rhythm] Charges becomes 0 on skill end

Secondary Skill - Drawing Come True
Throws a wall forward push and hit enemies within 5m
Wall creates a passive field [Blank Domain] on the floor lasting for 10s

Ink Spirit
Ink Spirit - The status while in Primary Ability
Ink Form - Primary Ability Name
Why.

Ink Domain
Donut ring dealing damage per .5s
In Primary ability it becomes a circle instead

Ink Rhythm
The bar under your primary ability icon
Caps at 30 unless in primary ability
[Ink Shade] & [Lingering Rhythm] Talent buff uses it
Used as a resource for attacking while in Primary Skill

Ink Shade
When at 15 (Half the bar), gain +25% RoF & -25% Reload time
(Does nothing in Primary skill)

Blank Domain
The white floor made by Secondary Skill
While inside...
- Gain 10 shield and 2 Rhythm Charges per second
- +30% Movement Speed
- [Ink Rhythm] will not decay

Really tldr;
Secondary skill to build bar / remove decay.
Half the bar will give you a buff.
Primary skill can be used as sustain, needs bar to hit enemies else it uses duration.
You have an AoE ring / Donut that does damage and changes based on if you're in your primary or not.

A more compressive guide of Momo (Mo Xiu) ability. I suggest reading the Skill description first.

Primary Skill - Ink Form
Attack (Ink Splash) uses 15 [Ink Rhythm] to deal 450 Ink Damage in a 5m AoE radius.
If you do not have enough [Ink Rhythm], consume 0.8s of skill duration for every missing charge instead.

Gets full [Ink Rhythm] on use, and passive cap unlocked.
Generate 2 Ink orb that gives 10 [Ink Rhythm] each.
Reduce Final Damage taken by 60%, on lethal hit, HP does not drop beyond 1 HP and remove 2s of skill remaining duration instead.
Reset [Ink Rhythm] to 0 when skill ends.

Secondary Skill - Drawing Come True
Creates a wall that pushes forward 15m that moves based on Momo's movement speed.
Enemies within 5m gets pushed back by the wall and being dealt 500 Damage.
Path created by the wall will create [Blank Domain] field for 10s.


Ink Spirit
Status when Primary Skill (Ink Form) is used.

Ink Domain
AoE passive, deal 75 Ink Damage per .5s.
Creates an outer ring around Momo at 8m to 16m. (Visuals can be disabled)
When in Primary Skill (Ink Spirit), the circle becomes 5m around Momo instead.

Ink Rhythm
The number you see on your Primary ability and the bar under it.
Passive charges that can provide [Ink Shade] & [Lingering Rhythm] Talent buff.
Also used as a resource for Primary Skill.

Ink Shade
Passive ability based on [Ink Rhythm]'s charges.
At 15 charges (Half charge, there is a line on the ability), gain +25% RoF & -25% Reload time.
(Does nothing in Primary skill, Ink Spirit)

Blank Domain
Ability field created by Secondary Skill, painting the floor white.
While inside...
- Gain 10 shield and 2 [Ink Rhythm] charges per second.
- +30% Movement Speed
- [Ink Rhythm] will not decay.