The door opens with the only resistance being the water. It leads to a room with four rotting supports with some rubble piled in the corner. Still invisible, the imp foes further into the room, seeing another room at the end of it. Only thing visible in the room being an open stone sarcophagus.

Hemmed in at the rear, Marasatra sees little but the backs of the others—until Ekko flits ahead, banking along the corridor and back again. Through the bat’s keening echoes she senses the hollow of a stone coffin yawning in the chamber beyond. An opened sarcophagus—never a friendly omen, she thinks, lips tightening.

“Gorin,” she calls softly, “something might lie in waiting by that coffin. Hold a moment.” Ekko swoops low, brushing the human’s forearm with a leather‑soft wingtip; a faint sigil of bone‑white script flickers on his skin and sinks in (Resistance vs. necrotic damage). “Jergal’s bulwark—should necrotic rot lash out, you’ll feel its bite dulled,” she explains, then adds to all, “If anyone needs steadier hands or keener aim, say the word; Ekko can carry a touch of Guidance where I cannot reach.” 

(Mara can hand out Guidance and Resistance through her familiar, please feel free to use and narrate that if you see fit, and if the situation permits–like when we are out of combat, etc.)

Meanwhile the invisible imp flutters into the sarcophagus chamber, peeking around for undead and other threats.

Stealth: 23
Perception: 16

Gorin, assuming you meant him although he is a human, thanks Marasatra before he moves forward, fiddling with some metal he brought with him. After which he places a tiny metal canon it on Zim's shoulder. Everyone feels protective energy flowing over him/her (10 temp hp).

"This should protect us a bit if a fight is gonna happen here." he says. After which he slowly moves into the room with the rottern supports to let the melee users walk past.

Action: Create Protection cannon, BA activate it.

((Does Vulnerability+Resistance mean normal damage?))

Quote from Secretfool >>

Gorin, assuming you meant him although he is a human, thanks Marasatra before he moves forward, fiddling with some metal he brought with him. After which he places a tiny metal canon it on Zim's shoulder. Everyone feels protective energy flowing over him/her (10 temp hp).

"This should protect us a bit if a fight is gonna happen here." he says. After which he slowly moves into the room with the rottern supports to let the melee users walk past.

Action: Create Protection cannon, BA activate it.

((Does Vulnerability+Resistance mean normal damage?))

 Ugh, my fault, I’m correcting his species, sorry. The spell Resistance doesn’t confer resistance, just reduces the specified damage type by 1d4 once per turn. 

Sarris will move forward (west) and search the room with the fallen rock pile and the 4 rotting wood columns -- allowing the others to move forward if desired.

Perception: 26

The room with the sarcophagus holds little else. The only other thing in the room is the broken cover of the stone coffin. Even inside the coffin only holds a skull and what looks to be a battleaxe.

In the room below just seems to be more rubble, even under the water. This room may have just been used to put the rubble while excavating the dungeon.

"No one touch that axe until someone can do a detect or other magic sense on it, just to be on the safe side."  Sarris adds after giving a rundown of what he found in his scouting of the chambers and rock pile.

"And I suppose we should be as careful about that skull in with the axe.  Never know when those things start floating and talking..."

As Mal has thoroughly scouted the sarcophagus chamber he telepathically reports back to his mistress who in turn informs the other Flaming Fist deputees about the situation in the chamber ahead. "There are no cultists there so as far as I can see we can move on from here now." She says but will patiently wait for the others to continue with their mission.

Marasatra steps over the threshold, gaze falling on the empty stone box and lone axe. “A single skull and a half‑rusted blade—gods, will this maze ever yield a proper Dead Three sanctum?” she mutters, irritation echoing off the wet walls. “I’ve seen morgue scrub‑rooms with more ceremony.”

[I'm unsure if her previous casting of Detect Magic is still in effect.]

She plants her staff, draws a fresh vial of silver ink, and glances around the party. “If you can spare ten minutes, I’ll scribe another sight‑sigil and confirm whether that axe is truly mundane—or merely pretending. Otherwise, we press on and hope the next corner offers something worth the effort.” (unless stopped she will search the vicinity with Detect Magic)

Sarris nods with approval, "Better safe than sorry.  Scry away, m'Lady."

He then goes south and stands to have a clear view up to the sarcophagus area and down the corridor they entered by... on guard, bow at the ready.

(If Mara wanted to take a look at it with detect magic (Spell is still active for 10 minutes) )

Looking at the sarcophagus, you see an aura of evocation emanate from it.

(If there's no further actions, then I assume the party goes back to the intersection and continues westward.)

Marasatra settles onto one knee beside the open coffin, jade-lit eyes sweeping its interior. She loosens a fist-sized bit of debris from the damp floor, balances it on the scalpel tip of her staff, and flicks it gently into the sarcophagus. The stone chips land with a dull splash, her gaze tracking every ripple of unseen energy. (Arcana to determine if it is a magical trap: 11, incl. Guidance; additionally she is trying to place rubble strategically to see if she can determine where it blocks the aura most in an effort to determine the most likely source, Investigation: 8)

She circles the coffin’s rim without letting skin touch stone, tracing faint sigils in the air and tilting her head as Ekko hovers near her shoulder—ears twitching at sounds no one else can hear. Marasatra rises, dusting grit from her gloves, and addresses the column in her calm, didactic cadence. “The evocation I perceive is localized to that sarcophagus and might be its content,” she explains, tapping the coffin’s rim with her staff for emphasis. “Evocation – being the school of force, flame, or thunder – often denotes two possibilities: either the weapon itself is enchanted to release destructive energy when wielded, or something is rigged as a proximity ward that detonates if the axe is disturbed.”

She paces once around the stone box, gesturing as though sketching diagrams in the air. “Consider it a dormant glyph on a handle. Remove it bare-handed and the spell may trigger; leave it and we forfeit a potentially valuable relic. Safe retrieval demands a remote lift—mage hand, hooked pole, or dispelling matrix—followed by containment in a sack of thick canvas until we can study it properly. Proceed accordingly,” she instructs no one in particular while stepping back.

"I hate to point this out but there is nothing in the mission description about looting old axes lying around in sarcophagi. As far as we can tell this part of the dungeon isn't even used by the dead three cult." The young red-haired patriar lady says a bit dryly from the other room. "How about this, we finish the mission and then those interested in generally plundering old catacombs can return down into this sewer and stay as long as they want?" She suggests with a forced smile.

Marasatra only lifts a shoulder in a delicate shrug. “Quite; the axe is no concern of mine—I examined it because our scout requested clarity,” she replies, voice even. Stepping back through the doorway she adds, “Judging by the rubble piled here, cult labourers used this chamber for spoil and plainly pried the coffin’s lid aside. That they left the weapon untouched suggests either deliberate avoidance or shared apprehension.” With that observation she retreats to the corridor, staff ready, and waits for the company to form up and press on.

Arkon takes a moment to stretch as he finally gets out of the tight hallway and into the larger chamber. Glancing at the axe, he gives a shrug. "A little small. We can take a better look once this is done," he agrees, moving next to Marasatra and waiting for the others.

"Why go back when we are here now." Gorin says, and he picks up the axe.

As Gorin picks up the axe, energy seems to seep out of it and form above the sarcophagus. It shapes itself into an battleaxe and it raises itself high in the air. Then a fierce roar fills the room as it goes for Gorin.

Roll For Initiative.

(Found this great png of a runescape axe. Also will add what the battleaxe is in Gorin's inventory.)

Sarris   Initiative:  14

Arkon initiative (w advantage from Remarkable Athlete subclass feature): 13