Timepiece

"Your friends are either going to die or turn into Seaborns."
"[...] And the survivors... become overwritten by their cells, becoming nothing more than another sea monster."
"<What? That's...>"
"<... not... a very big deal?>"
"<We should just kill them before they turn.>"

You, through some way or another, have had your head replaced with a magic clock that can become synced with the time of certain people, and then rewind them if they were to take fatal damage.

Sinner #10 - Level 3

"Woah, that fire on your head's not hot at all? Fascinating stuff..."
"Lotsa ticking and tocking going on, that's supposed to sound like them talking to you folks, huh?"

The Timepiece
Your head is replaced with a magic clock. When you speak, the only thing people can hear is clock noises. But you are immune to the Blinded, Deafened, and Charmed conditions. You can still perceive things as if you had a normal head.
During a short or long rest, you can designate up to 12 creatures to become 'Sinners'. Creatures designated as Sinners can hear and understand your voice normally (even if you do not share a language), and you know the general locations of your Sinners at all times.
A Creature remains a Sinner until you designate them as not being a Sinner anymore during a short or long rest.

Rewind the Clock
As an action, you can Rewind the Clock. Each Sinner restores a number of hit points equal to the difference between their current hit points and their hit point maximum, and then you take damage equal to a quarter of the hit points restored in psychic damage. If there is a Sinner that is unconscious, they heal to full and stand up. If there is a Sinner that is outright Dead, they are revived at full health with 0 failed death saving throws. When healing a downed or dead sinner through this feature, you take damage equal to half the hit points you restore for them instead of a quarter.
This damage cannot reduce you below a number of hit points equal to your Sorcerer level.
The Psychic damage from this feature treats immunity to Psychic damage as resistance.

Golden Bough Resonance - Level 6

<I mean, my clock or the Golden Bough... or whatever it is... can turn back time...>
<... then what's there to say that I can't accelerate it or shorten it?>
"We're... faster. Fast enough to outrun our enemies!"
"This is not temporal acceleration, to be precise. It would be more accurate to say we are in a temporal deceleration field that slows everything except us in a certain radius."

Durante - Pigritia
As an action, you can expend 3 Sorcery points to tap into a hidden power of your Clock and activate this feature. When you activate this feature, all creatures within 80 feet of you have their Movement Speed and their Dexterity modifier halved (rounded down). If a creature's dexterity modifier is 0 or less, their dexterity modifier is unchanged. This effect lasts for 3 turns, and your Sinners are immune to this effect.

Clockwinding
When one of your Sinners reduces a creature to 0 hit points, you regain 1 sorcery point. This can happen once per sinner per turn.
At level 10, if a Sinner would have their movement speed reduced by a magical effect, or would become unable to move as a result of Haste ending, that effect is negated.

The Surrendered Witness and the Ended Dream - Level 14

There stood Sancho, standing tall even as her body was torn by the brutal, sanguine lance.
Unbroken and bold, unyielding before the First Kindred's insurmountable might.
The same back I always saw scampering toward inevitable trouble whenever something interesting was happening. [...]

Durante - Superbia
As an action, you can expend 4 Sorcery points to activate this feature. When you activate this feature, select 1 Sinner. The next time the Sinner uses a limited-use feature, such as a Fighter's Action Surge or a Cleric's Channel Divinity, it is used without expending a use.

Durante - Morositas
Under Mercy, All shall be made Equal
As an action, you can expend 6 Sorcery points to activate this feature. When you activate this feature, average the Melee Attack bonus, Ranged Attack bonus, Spell Attack bonus, and spell save DC of all creatures within 80 feet of you. For 3 turns, each creature's respective bonus or DC is fixed to the corresponding average, rounded down. Your Sinners have their bonuses and DC increased to 1 more than the average for the duration. The average values are only calculated when this feature is activated.
Note; The values are averaged with only the respective bonus. Melee Attack bonus is averaged with Melee Attack bonus, Spell save DC is averaged with Spell save DC, and so on. Only creatures with a corresponding bonus or DC contribute to that average.

The Unsevering - Level 18

It's true that the threads will keep multiplying the more Ryoshu cuts at them...
If that's the case... perhaps a chain will work instead. The same chain she already cut off, the same stubborn one that brought her back from death countless times...
Melt down the severed chain and reforge it in the roaring kiln of one's heart
<Take this chain at let it guide your way.>
<Go and tell her... Tell her everything you never got to say.>

Durante - Ira
As an action, you can spend 8 Sorcery points to activate this feature. When you activate this feature, select 1 Sinner. Until the end of your next turn, the Sinner's Weapon and Spell attack bonuses increase by 2, whenever they deal damage, they roll one additional damage die, and their Hit Points cannot drop below 10.

Used to this
You gain resistance to Psychic damage. Rewinding a Downed or Dead Sinner has you take damage equal to a quarter of the hit points they heal instead of half.