"Hah, what did I say, a guardian, not quite what I expected though I admit." The dark-haired young woman says with amusement and quickly unleashes a divinely radiant beam of eldritch crackling force towards the shapechanging monstrosity.

Eldritch Blast: 19 Force: 12

She then retreats out of the chamber if it can be done without coming to close to the monster.

Meanwhile Thoth flies closer to distract the shapechanging monstrosity.
(Dodge)

So startled is Ophelia as the horrifying mimic shatters her reverie of magic and death that she nearly leaps away in alarm, only recovering herself in time to snatch her dagger from its sheath at her waist with an undignified yelp and swipe at the slavering creature, her blade suffused with violet arcane energy.

Movement and Bonus Action:  None - Ophelia is too startled.

Action:  Ophelia casts True Strike using her Dagger:
True Strike with Dagger to hit:  17
True Strike with Dagger damage:  8 (radiant)

(Tides of Chaos marked as expended on Initiative.)

If the mimic attacks her, Ophelia will use her Lucky feat to impose disadvantage on the attack (unless already disadvantaged, for example due to Zephirah's Vicious Mockery or Satina's Sap Mastery below).  Ophelia also has the Shield spell as a reaction and may use it.

Zephirah jerks back until sandstone kisses her spine, the viol bow clutched like a talisman. “Great Nethys, how long has that thing been fasting—since the last dynasty?” she blurts, voice quavering into sarcasm. Drawing a sharp breath, she flicks the bow across two strings, the notes twisting into a thin, cutting sneer that crackles with psychic bite.

“Come now, sarcophagus-for-brains—were you always this hungry, or did the centuries just leave you with nothing but an appetite?” The taunt spirals toward the mimic, laced with the sting of Vicious Mockery (Wisdom save DC 14 for 2 psychic damage).

Satina quickly grabs her flail and steps forward to strike the mimic. 
(Flail Attack: 17, Damage: 12 bludgeoning; Sap: if hits - target has Disadvantage on its next attack roll before the start of my next turn.)

"Ophelia! You should get back if you can!" she shouts with a hint of concern. 

"Hah, what did I say, a guardian, not quite what I expected though I admit." Nephthys says with amusement and quickly unleashes a divinely radiant beam of eldritch crackling force towards the shapechanging monstrosity. Her beam strikes the creature directly in one of its shifting eyes, eliciting an otherworldly scream (hit!) She then retreats out of the chamber if it can be done without coming to close to the monster. Meanwhile Thoth flies closer to distract the shapechanging monstrosity.

So startled is Ophelia as the horrifying mimic shatters her reverie of magic and death that she nearly leaps away in alarm, only recovering herself in time to snatch her dagger from its sheath at her waist with an undignified yelp and swipe at the slavering creature, her blade suffused with violet arcane energy. The blade rakes across the strange flesh, leaving a wound of weeping, dark blood (hit!).

“Come now, sarcophagus-for-brains—were you always this hungry, or did the centuries just leave you with nothing but an appetite?” Zephirah’s taunt spirals toward the mimic, laced with the sting of Vicious Mockery. It shudders under the discordant energy of the spell (failed save!).

Satina quickly grabs her flail and steps forward to strike the mimic. Her weapon slaps into the creature with a disquieting squelching noise (hit!).

One of the mimic’s pseudopod’s lashes out at Satina, but fails to find purchase on her armor (miss).

Initiative (bold may act):

1. PCs
2. Enemy

Nephthys unleashes another divinely radiant beam of eldritch crackling force towards the disgusting monstrosity.

Eldritch Blast: 9 Force: 6

 Meanwhile Thoth keeps fluttering around to distract the monstrosity.
(Dodge)

Zahara does not flinch.

The grotesque shape of the mimic appears with a lurch, ancient dust curling around its gnashing, wet mouth, and though the others react with steel and sarcasm, she simply lifts her staff.

“Blasphemous thing,” she murmurs, voice calm and razor-sharp. 

She thrusts the tip of her staff forward, her fingers weaving a swift and practiced sigil in the air beside it. A sudden spark flares to life in her palm, then streaks forward as a searing bolt of fire, the light of it painting the carved columns in flickering gold.

The Fire Bolt arcs across the chamber, heat rippling in its wake as it sails toward the mimic’s writhing mass. 

Action Cast Fire Bolt 13 to hit, 3 fire damage

Zephirah watches the mimic’s flailing pseudopod slap uselessly off Satina’s shield and lets a knowing grin curl across her lips. “Oh, poor relic—you’ve slept a thousand years and still can’t land a proper swing?” She flicks her bow for a single, dissonant scrape, the sound knifing through the air like broken granite. “Perhaps those stone jaws are just for show—much like the pharaoh’s titles on these walls!”

The barbed quip rides the screeching note, unraveling into another burst of Vicious Mockery aimed straight at the monster’s fragile ego (Wisdom save vs. DC 14 or 1 psychic damage).

Like a recalcitrant child set in her course of action even when admonished otherwise (by Satina), Ophelia continues her somewhat comical arcane dagger attack on the mimic's grotesque form, her blade still glowing with violet energy, as if angered by the creature's deception.

"Why, you can smile, and murder whilst you smile,
And cry 'Content' to that which grieves your heart,
And wet your cheeks with artificial tears,
And frame your face to all occasions..."

Movement and Bonus Action:  None - Ophelia is no longer startled, but too focused on the mimic to relent in her peeved assault.

Action:  Ophelia casts True Strike using her Dagger:
True Strike with Dagger to hit:  23
True Strike with Dagger damage:  8 (radiant)

If the mimic attacks her, Ophelia will use her Lucky feat to impose disadvantage on the attack (unless already disadvantaged, for example due to Zephirah's Vicious Mockery or Satina's Flail Sap Mastery).  Ophelia also has the Shield spell as a reaction and may use it.

Satina gives Ophelia the briefest of glances as she keeps fighting at her side. She then steps in to make another strike against the mimic.

(Flail Attack: 14, Damage: 12 piercing)

Nephthys's blast arcs wide, blasting into a column (miss).

Zahara’s Fire Bolt arcs across the chamber, heat rippling in its wake as it slams into the mimic’s writhing mass (hit!).

Zephirah’s song seems to soar over it--perhaps it’s too distracted by being burned and bludgeoned (success).

Ophelia continues her somewhat comical arcane dagger attack on the mimic's grotesque form, her blade still glowing with violet energy, as if angered by the creature's deception. It stabs viciously into the creature’s jelly-like mass (hit!).

Satina’s flail swings around again and crushes the creature into into a disgusting mess (hit!). 

Having made quick work of the mimic, the party notes the existence of two hidden doors, one to the north and one to the south. To the west, those with darkvision can make out a dark statue standing sentinel in a wide chamber.

(Actions?)

As soon as it is clear the mimic has been felled, Satina turns to Ophelia. "Are you alright?" It didn't seem like she had even been attacked, but she just wasn't sure. "That was...  interesting the way you fought there. Well done." 

"I'm not sure we learned anything about our options for continuing. I say we pick one of the hidden doors. The one to the north?" she suggests. 

Standing there a little breathless, Ophelia gives what is now the messy corpse of the sarcophagus-imitating mimic one more desultory swipe with her True Strike-infused dagger, as if still peeved at the non-magical deception of the creature's concealment in plain sight.  Only then does she look sheepishly up at Satina and down at her weapon, still glowing with violet, and shrugs with a weak smile, unsure herself of how the magic really works.

She gestures at the dead creature with her dagger as she sheathes it, still faintly glowing, her voice almost lucid (in a fashion) for the moment.

"From flail and blade and fire flung,
Through arcane blast and derisive tongue,
Lies dead the liar on the stony floor,
As we choose door from secret door.
Not yet, not yet has our fate been sung..."

Ophelia looks ready to follow her companions through whichever door they choose.

"Sounds good." Nephthys says as she comes closer to watch the revolting mess of the shapechanging monstrosity on the chamber floor, then nodding, ready to move on, and so is Thoth. "Imagine this creature has been waiting here for ages and ages, it must have been hungry indeed." She says with grin and a wink to Zephirah. 

Perception to see if there is anything in the mess not fully devoured by the monster: 22

Zephirah wipes splashes of mimic-ichor from her bow hand on a kerchief, then studies the muralled walls a moment longer, tracing a few chipped hieroglyphs with a thoughtful hum. “North, south—six of one to me,” she admits with a loose shrug. Still, curiosity tugs westward: she pads to the very edge of the open passage, plants her back against the jamb, and leans just far enough to let her tiefling eyes drink in the gloom. Holding her breath, she lets one fingertip pluck a single muted note on the viol—testing the chamber’s echo—while she squints at the distant statue’s silhouette, careful not to set foot beyond the threshold of her current chamber. (Perception 10)

Nephthys does not find anything notable in the mess in this room.

Ahead to the west, Zephira sees a black granite statue of a pharaoh standing on the polished alabaster floor in the center of a chamber beneath a vaulted limestone ceiling decorated with gilt stars. An engraved panel of granite stands against the western wall, carved to resemble a door. A flat granite slab lies on the floor in front of the false door.

Zephirah eases back from the threshold and motions the group closer. “Black-granite pharaoh, center stage, our host –if I had to guess– seems to be standing vigil,” she murmurs. “Ceiling painted with gilt stars; looks ceremonial. West wall holds a false door—engraved stone, with a flat slab laid like an offering before it, perhaps an altar?” She slings the viol behind her and raises an eyebrow at the twin hidden doors flanking the chamber. “So—do we pay our respects to the stone sovereign, or see where these secret passages lead first?”

Ophelia points silently at the flat granite slab in front of the door, her brow furrowed.  Clearly concerned that it might be another trap.

She steps near it (without touching the slab or door) to attempt to sense whether her Detect Magic aura senses anything.  She also begins to take her spectral Mage Hand and presses down on the slab, simulating a ten pound force, unless someone forestalls her.

At Ophelia’s cautious gesture and the soft press of her Mage Hand upon the slab, Zahara spares a glance but does not approach. Her eyes linger on the false door and the statue that. “False doors may punish curiosity,” she murmurs.

She approaches the northern wall, but pauses, her eyes returning to Ophelia’s spectral hand as it tests the granite slab. “If that slab triggers nothing,” she says softly, “then I’ll try this door.”

Zahara waits, still as a statue herself, until the results of Ophelia’s test are known. Only if no trap is triggered does she press her hand to the wall, ready to open the door to the north.

Nephthys would await the outcome of the ongoing investigations, but Thoth flies closer to the next chamber to peek inside, curious to see every chamber inside the pyramid.

Thoth History if relevant: 8