Drogen attempts blasting the wraith with another guiding bolt, followed up by another whack with his spiritual weapon.

Guiding Bolt to hit: 15 damage: 20

Spiritual Weapon to hit: 16 damage: 7

     Thunk attacks.  Once done, Thunk drops a shortsword and grabs the sword hilt from out of the stone box. "How would this help?  Or you mean the body?" Thunk asks.

Shortsword Attack: 19 to hit for 12 damage
Bonus Action SS Attack:  14 to hit for 3 damage...

Arokas hasn’t lost any hit points so he feels nothing after his spell misses except frustration. He assumes whatever happened was just a coincidence and resorts to casting a Magic Missile.

Damage: 9 force damage

Tanis does not really know the answer to Thunk's question.  He looks at the sword hilt that the orc grabbed from the sarcophagus, befuddled.

"Maybe it is a magic sword?  Ah... is there a way to make the blade appear?"  Voice we hear.. where are you?  We opened the sarcophagus.  Can you help?

And what was the thing on the floor that the unicorn just tripped over?  And where did the unicorn come from anyway?

Shaking his head in confusion, Tanis continues the barrage on the wraith.

Action:  Hand crossbow attack:
To hit wraith:  21
Damage plus Hunter's Mark:  8 + 4 = 12 piercing

Bonus Action:  Crossbow Expert hand crossbow attack:
To hit wraith:  16
Damage plus Hunter's Mark:  8 + 4 (same!) = 12 piercing

Drogen's bolt finds the undead, but as he cast his spell everyone in a 30ft radius from him feels their life being sucked away as they take necrotic damage (4 to Derendil, 9 to the unicorn, 1 to Thunk and 1 to Arokas) that heals Drogen (for 15 hp total). The spiritual hammer finally makes contact with the undead, disappearing after the hit.

Thunk hacks twice at the wraith, who is barely holding onto existance at this point. As the orc grabs the sword handle from the corpse, a blade of pure radiance springs from it. Bright sunlight shines in a 15ft radius from it and dim sunlight for the next 15ft. The undead visibly recoils as the light reaches it. Thunk can hear the familiar lady's voice in his head "you have my thanks, hero. My name is Dawnbringer, let's put this undead to eternal rest!"

The voice is still speaking to Thunk when a barrage of missiles from Arokas hits the wraith, finishing it off for good. The sorcerer feels a connection to the ethereal plane. For the next minute, he can teleport up to 20 feet as a bonus action on each of his turns.

Initiative order:
21 Derendil (32)
19 Wraith (78)
14 Unicorn (9)
13 Drogen
11 Thunk (1)
11 Arokas (1)
  7 Tanis

Tanis goes next.

OOC: too many things happened for Tanis turn to make sense. @Tybard you can choose what to do next. The unicorn is still there, looking in pain due to the necrotic damage she took from Drogen's wild surge and satisfied that the undead is not here anymore.

Tanis, now visible in the light of Thunk's new magical blade, walks to the room's center looks around carefully, both for any still-lurking enemies AND for whatever it was that the unicorn had tripped over during her charge.

Tanis Perception:  19

(In Elvish and then Dwarvish so that everyone in the room, including hopefully the unicorn can understand):
"Is everyone all right?  And does anyone still hear the voice?  Was it coming from... from that radiant blade?"

Belatedly remembering his manners, Tanis turns to the unicorn and bows deeply.

"Celestial one, I am Tanis Shaidaro and these are my companions Thunk, Drogen, Arokas, and Derendil who... is an elven prince despite his appearance.  We are trapped deep underground, escaped prisoners of dark elves, under the continent of Faerun, in the world of Toril in the material plane.  There is strange, wild magic here which seems to flare when any of us casts a spell.  I believe such magic may have summoned you?  For that I am sorry, as we ourselves are on the run.  We only explored this tomb of Brysis from ancient Netheril because we heard a woman's telepathic voice asking for rescue.  It may instead have been this radiant blade my companion now holds.  We did not expect all these undead who attacked us.  Thank you for your aid."

Arokas recoils from Drogen pull of necrotic energy, and is shaking uncontrollably as he feels some kind of connection form between him and something unknown. Without meaning to, his magic pulls on that connection and Arokas teleports into the room below, huddled in a corner. “Wh-wha-what did you do to me?” Arokas asks, looking at Drogen with fear in his eyes. “D-d-don’t EVER cast something on me by surprise!”

(common) "I didn't do that ...that wasn't how my spell is supposed to work." Drogen replies.

     “Their name is Dawnbringer,” Thunk says in answer to Tanis.  “And they say I’m a hero!”  Thunk smiles bigly and gives the blade a couple experimental swings…

Quote from Tybard >>

Tanis, now visible in the light of Thunk's new magical blade, walks to the room's center looks around carefully, both for any still-lurking enemies AND for whatever it was that the unicorn had tripped over during her charge.

Tanis Perception:  19

(In Elvish and then Dwarvish so that everyone in the room, including hopefully the unicorn can understand):
"Is everyone all right?  And does anyone still hear the voice?  Was it coming from... from that radiant blade?"

Belatedly remembering his manners, Tanis turns to the unicorn and bows deeply.

"Celestial one, I am Tanis Shaidaro and these are my companions Thunk, Drogen, Arokas, and Derendil who... is an elven prince despite his appearance.  We are trapped deep underground, escaped prisoners of dark elves, under the continent of Faerun, in the world of Toril in the material plane.  There is strange, wild magic here which seems to flare when any of us casts a spell.  I believe such magic may have summoned you?  For that I am sorry, as we ourselves are on the run.  We only explored this tomb of Brysis from ancient Netheril because we heard a woman's telepathic voice asking for rescue.  It may instead have been this radiant blade my companion now holds.  We did not expect all these undead who attacked us.  Thank you for your aid."

The unicorn turns her attention to the recently visible Tanis and replies (elvish) "I can sense the Weave beign disturbed in this location. The spell that brought me here was powerful, but chaotic." You see her horn shimmer for a moment and her face no longer shows any pain. Before you can exchange more words, she disappears as suddendly as she arrived.

Looking at the place where the unicorn stumbled, Tanis notices a small area where the floor has no dust. Walking over to the spot, he can touch an invisible stone chest just two feet away from the sarcophagus.

With the light coming from Dawnbringer you notice that the sarcophagus cover that Derendil ripped apart is a thin sheat made of pure gold, untarnished by time. The wall behind it has a carved inscription in ancient elvish noting that this is the final resting place of Brysis.

Quote from Kaemgen >>

     “Their name is Dawnbringer,” Thunk says in answer to Tanis.  “And they say I’m a hero!”  Thunk smiles bigly and gives the blade a couple experimental swings…

For a blade made of pure light, Thunk finds it perfectly balanced. In his head Dawnbringer keeps chattering "finally out of that terrible, oppressing darkness. I can't wait to see the sun shining again over Netheril."

Disappointed but not surprised at the wild magic-summoned unicorn disappearing as quickly as she had appeared, Tanis turns to his companions.

(Dwarvish):  "The blade suits you, Thunk.  Dawnbringer!  She is right, you are a hero.  Does she still speak in your head?  I do not hear her any more."

(Dwarvish and repeating in Elvish):  "I suppose the wraith was what was left of Brysis and those other four were her... maidservants?  The blade was who spoke in our minds, asking for rescue, which we have done.  The valuables here, I feel no guilt at taking since their former owner attempted to drain our lives.  But also, there is an invisible chest here on the ground that the unicorn stumbled on when she charged."

Cautiously, attempting to sense for traps to the extent he can (previous Perception check), Tanis checks if the invisible chest is locked.

     "She is here," Thunk answers in dwarvish as that is how the question was asked.  "In the sword.  In my head.  She happy to be lighted up again.  Happy to not be alone no more."

     After a moment Thunk frowns and adds "She uses big words.  Thunk will teach her small ones..."

     Thunk is confused about invisible chests that Tanis knows about but that can't be seen so Thunk does what he can, searching the sarcophagus and things that can be seen, not afraid to disrupt or dismember the body in the stone box if need be.

Investigation:  11

Since you already took Dawnbringer out, Brysis' sarcophagus only has her corpse in simple robes.The gold cover could be rolled up or folded for transport.

The invisible stone chest next to it is filled out to the brim with treasure. As you take things out they become visible. You find thousands of coins, one in five of them is a gold coin, the rest are silver. There are also eleven zircons, a brass necklace with 4 red beads hanging from it, and two potions. One contains rose-hued, effervescent liquid and the other red liquid.

Derendil looks flabberghasted at the disappearing unicorn (elvish) "such a majestic creature." Turning his attention to more immediate matters he looks at the pile of coins taken out of the treasure with a glimmer in his eyes (elvish) "with this coin we may find it easier to purchase safe passage to the surface."

“Alone,” Arokas whispers, having calmed down from his panic. “Sometimes, I wish I was just left alone. Live out my life in solitude. No one to hurt me.”

Tanis looks at Arokas for a long while and blows out a long breath.

"I understand how you feel, though I have always sought out company, not solitude.  If you have been hurt in the past, I am truly sorry.  But solitude is not always solace.  Consider Brysis, alone in this chamber for millennia and how she turned out.  We on the other hand still live and forge ahead..."

The ranger begins gathering and handing the loot (other than Dawnbringer) in a business-like fashion.
- To Arokas, he hands the brass necklace with 5 red beads.
- To Drogen, he hands the two potions, one rose-hued and effervescent, and the other with red-colored liquid.
- To Thunk, he rolls up and hands over the thin, pure gold cover of Brysis' sarcophagus.
- To each of the five people here, including Derendil and himself, he scoops from the treasure 200 gold pieces and 200 silver pieces, leaving the rest.
- To Derendil, with his strength and carrying capacity, he hands the small, invisible chest itself, containing the rest of the coins.
- To each of the five people here, he hands two zircons, keeping three for himself to account for all 11.
- Tanis himself gathers up the crossbow bolts he has shot during combat, from this chamber and the one above so as not to waste them.

"I hope that seems fair.  Arokas and Drogen, perhaps you can study these items further to determine whether they have magic capabilities as Dawnbringer clearly does.  But we have to keep moving and rejoin the others.  The dark elves may still be tracking us.  We have rescued who we came to rescue.  Who knows what other undead lurk here in this ancient Netherese tomb.  Sarith is probably still up there, staring vacantly off into nothing."

     "We're trying to not be seen," Thunk explains to seemingly nobody.  "Sorry but I think...  I know, I know...  But... But..."

     Thunk sighs in annoyance and frustration.  "Maybe one of you can explain it to her?" Thunk asks as Tanis is making little piles of the shiny coins and other goods he pulled out of seemingly nowhere.  

(common) "Aye, I know the proper spell that can tell us what these items are but I lack the proper spell component to cast it. Should we come across a pearl on our travels let me know." He answers Tanis after taking his share of the loot.

Arokas takes the necklace and his gold, and studies the necklace, trying to perceive any arcane presence and decipher what it could be.

Arcana: 5

Seeing that Thunk lacks a container to store his coins, Tanis scoops the orc's share back into the chest that Derendil carries.

(Dwarvish) "Some of that is yours, Thunk, but you carry the chatty glowing blade, and Derendil here will carry your share for now.  I don't know what to tell her since I can't hear her.  You will have to think of something, but for now, we have to get back out to find the others and keep moving."

Tanis suits his actions to his words, clambering out of the room and carefully back out the stairs, watching for more undead or other enemies or hazards.