Muirgurn will cast healing word on Peter (gains 7hp) and the cantrip sacred flame on Skeleton 4 (DC13 Dex save or 6 radiant damage).

(NB the following is my estimate of the field of battle, the DM may adjudicate differently!)

The Tower of Zenopus: 16 (round 3)
==================================
17: Razil Trympan <7/10 HP> (AC 13)
# 16: Aldrich Garen <10/10 HP> (AC 16, Mage Armor)
15: Skeletons
- Skeleton 1 <Bloodied>
- Skeleton 2 <Healthy>
- Skeleton 3 <Healthy>
- Skeleton 4 <Injured> (Shortbow)
14: Peter Killian <8/8 HP> (AC 14)
9: Muirgurn Fettercairn <6/12 HP> (AC 18)

(OOC:  For record keeping, I'd be at +4 temp HP if I did actually kill that skeleton)

Never mind about the death save, Peter. You were unconscious on your turn but then are revived by Muirgurn's healing word with 5 hit points (roll 2 + Muirgurn's Wisdom mod. 3) and are now lying prone on the dusty floor.

Skeleton 4 tries to avoid the descending radiance. Dexterity save: 15

Razil's dagger again penetrates the skeleton's armor, but it still stands. (I roll monster hit points.)

Aldrich swings his longsword at the skeleton in front of him. Attack: 7 Damage: 11

Skeleton 1 attacks Razil. Attack: 15 Damage: 6

Skeleton 2 leans over Peter and stabs with its sword. Attack: 10 Damage: 6

Skeleton 3 attacks Aldrich. Attack: 14 Damage: 4

And Skeleton 4 shoots again at Muirgurn. Attack: 21 Damage: 7

Skeleton 4 is engulfed in radiant flames as some of the negative energy that animates it is burned away.

Aldrich's longsword deals Skeleton 3 a mighty blow.

Skeleton 1 and Skeleton 3's shortsword stabs are easily avoided by Razil and Aldrich.

Skeleton 2 drives its sword into Peter lying on the floor, who is once again unconscious.

And Skeleton 4's arrow glances off Muirgurn's scale mail.

Peter, once again on your turn make a death saving throw.

Sorry, I just realized that by skipping over Peter's last death save, I didn't give him a chance of regaining consciousness on his turn and taking a turn, so make two death saves, one for last round and one for this round, and we'll retcon anything that needs it.

Muirgurn will again cast healing word on Peter (gains 7hp), muttering darkly about humans and their frail constitution, then attempt to engulf Skeleton 4 with sacred flame (DC13 Dex save or 1 radiant damage).

(Spell slots expended!)

Hoping his dagger strikes true again, Razil strikes out with his dagger again attempting to fell the skeleton in front of him.

Attack: 16 Damage: 5 

death save 1:  13  death save 2:  17

Okay, so everything is as it was described. Peter, lying prone on the floor, is once again revived by Muirgurn's healing word, regaining 6 hit points, rather than 9. (Not sure why you keep adding 6 to your roll, Muirgurn. Your spellcasting ability (Wisdom) modifier is +3.)

Skeleton 4 attempts to dodge Muirgurn's radiant flames. Dexterity save: 10

Razil's dagger plunges into the skeleton, breaking the spell of unlife that animates it, and it crumples to the ground, a jumble of scraps of armor and bone, while Razil gains his dark one's blessing.

Aldrich attempts to finish off Skeleton 3. Attack: 20 Damage: 3

Skeleton 4 gets caught in the flame, and it howls in pain as its animating energy is burned from within.

Skeleton 3 is hit by Aldrich's longsword but fights on.

Skeleton 2, seeing Peter revive, lying prone on the floor, once again tries to finish him off. Attack: 21 Damage: 4

Skeleton 3 strikes back a Aldrich. Attack: 11 Damage: 4

Skeleton 4, seeing Skeleton 1 fall, drops its bow and moves forward to join the melee, drawing its sword and attacking Muirgurn. Attack: 18 Damage: 3

Peter is hit again and still prone but remains conscious this time.

Aldrich again avoids being hit.

Muirgurn's armor is penetrated by Skeleton 4's shortsword.

The triangle is the bones of the fallen skeleton, which is difficult terrain.

Everybody can go now.

Peter staggers to his feet, gently rocking, fresh out of unconsciousness, and not far from returning.  He rubs some blood from his lip, and flings his blade under the ribs of the skeleton ( skellly 2) in a half hearted last stand (( 6 to hit, doing 9  piercing damage))

Muirgurn wields his warhammer against Skeleton 4: Attack: 17 Damage: 3

Razil sheaths his dagger and surveys the scene.  Seeing Peter in seemingly poor condition, he raises his hand, utters some arcane words, and lets out an Eldritch Blast at Skeleton 2.

Attack: 19 Damage: 1 

Aldrich will swing his longsword at skeleton 3 followed by his shortsword
attack longsword: 12, damage if hit: 6
attack scimitar: 19, damage if hit: 8

edit: i just realized that for two-weapon fighting both weapons need to be light. realizing that, i would like Aldrich to cast frostbite at the same target. If im allowed to change, then it has to succed on a dc12 con save or take 1d6 cold damage and have disadvantage on the next attack it makes.
Im gonna leave the second roll to keep it clean though (no warning about modified rolls)

Peter's rapier stabs air as it goes wide of Skeleton 2.

Muirgurn's warhammer demolishes Skeleton 4's skull, reducing the undead creature to a pile of rubble.

From where you stand Razil, Skeleton 2 has 3/4 cover from your eldritch blast because of Muirgurn and Peter being in the way, but even if you had moved, it would have bounced off the skeleton's armor. As it happens, your crackling beam of energy is narrowly dodged by Muirgurn after it gets past his shield.

Aldrich, I hadn't considered that you had meant to use two-weapon fighting with your two swords. If you still want to, we can retcon that your longsword is a shortsword (or another scimitar) instead. If not, I'm unclear if your intention is to replace both sword attacks with your cantrip (which you can do), or if it's to attack with your longsword and cast your cantrip. This would require two actions, which I don't think you can do. I'm unclear because of what you said about the second roll but not the first, so please clarify this for me.

Edit: To be clear, your options as I see them are to attack with shortsword and  scimitar (or two scimitars), attack with your longsword only, or cast your cantrip only. 

(i would really appreciate to replace the longsword with another scimitar. i was intending to use two weapon fighting, but when i created the character i missed a detail in the rule and got a longsword. Im going with the weapon attacks for now (two scimitars), and feel free to "heal" the skeletons aldrich hit by 2hp as they were actually hit by a scimitar)

Aldrich, your last scimitar strike drops Skeleton 3 to the ground.

The last skeleton standing (Skeleton 2), intending to fight to the death, tries to take advantage of Peter's overextended thrust and stabs at him with its sword. Attack: 10 Damage: 8

The skeleton also misses its sword thrust, lunging at a spot just beside Peter.

Sorry, this one came out a little blurry. (Replaced. Hopefully this one's better.)

Everybody go.

Razil winces slightly as he watches his bolt pass dangerously close to Muirgurn.  He makes his way past the rubble of the skeleton he defeated, and with this skeleton in plain view lets loose another Eldritch Blast.

Attack: 18 Damage: 2