With his magical energy running low, Lothlién shoots a Fire Bolt at the ghoul.

Attack: 19 Damage: 13

After that, he steps away, trying to get the fireplace between himself and the ghoul, so he's not flanked by whatever is coming.

Fire finishes the ghoul that hid behind the throne. But before you get a moment to recover your breath, six more of the undead creatures crawl out of the fireplace on the west wall. The three undead in front of the group manage to get close enough to try to bit you.
Attack: 12 Damage: 8 against Lia.
Attack: 8 Damage: 8 against Lothlién.
Attack: 21 Damage: 8 against Xarroth.

Initiative order:
18 Xarroth (in melee with a ghoul)
17 Rhok
12 Lothlién (10, in melee with a ghoul)
10 Six ghouls
  6 Lia (in melee with a ghoul)

Lia goes next.

 OOC: I have no idea what's going on with the dice roller, I could swear that the damage against Lothlién was 10 when I first looked.

Lia casts misty step to put her companions between her and the new ghouls. She then casts mind sliver
Targetting the ghoul that tried to attack her.
DC 14 Int save, or take 3 damage and suffer the spells other affects.

The very image of Xarroth shatters and crumbles away in silver scales and re-appears with a flash of silver light a breath later next to Lia. A huff of flame from the dragonborn is caught within his claws and condensed into a mote of flame that is sent towards the ghouls, splitting into two in the air as it flies!

Bonus Action: Misty Step
Fire Bolt
Twinned
Bolt #1: Ranged Spell Attack: 9 Damage: 12 (fire)
Bolt #2: Ranged Spell Attack: 18 Damage: 11 (fire)

.

Rhok, acknowledging the extra threat, casts cure wounds on himself

healing (first action):   7   

Then rushes at the new enemies, short sword drawn and attacks the nearest ghoul:  Attack: 14 Damage: 5  

if that enemy has taken damage, add colossus slayer damage:  4  

as he rushes in, he asks "Does anyone need a small bit of healing? I have one heal left"

Lothlién concentrates on the nearest enemy, his eyes turning to dull white while he mumbles magic words, clenching his hand into a fist; at the same time, a phantasmagoric hand reaches the ghoul!

Chill touch:Attack: 9 Damage: 9; target has disavantage when attacking me until my next turn

He also shouts for his allies "I still have energy for one fireball, if you guys think it's worth the risk!"

EDIT: spending one Empowered spell to reroll that 1: 2

Int save against mid sliver: -1

The ghoul attacking Lia lets out a shriek as she disappears, clutching its head in pain as the spell affects it. Xarroth leaves behind an equally confused ghoul, now smoking from the fire. Rhok rushes the burnt undead, taking an arm out of it with his short sword. Lothlién focuses on the menace in front of him, damaging it with a spell.

Initiative order:
18 Xarroth
17 Rhok (in melee with a ghoul)
12 Lothlién (10, in melee with a ghoul)
10 Six ghouls (9, -1d4 next save) (20) (10, disadvantage next attack)
  6 Lia

The gouls retaliate, first the two that are already facing people.
Attack: 21 Damage: 10 against Rhok.
Attack: 8 Damage: 12 against Lothlién.

The other ghouls quickly limp around the room, focusing on the people they see closer.
Attack: 19 Damage: 5 against Rhok.
Attack: 10 Damage: 10 against Lia.
Attack: 18 Damage: 10 against Lia.
Attack: 19 Damage: 13 against Lothlién.

Initiative order:
18 Xarroth
17 Rhok (in melee with two ghouls)
12 Lothlién (10, in melee with two ghouls)
10 Six ghouls (9, -1d4 next save) (20) (10)
  6 Lia (17, in melee with two ghouls)

Lia casts shield deflecting both attacks.

She then casts mirror image increasing her protection.

"Excellent cast, Lia!" Xarroth exclaims as a Fire Bolt sent towards the ghouls, splitting in the air, aimed at the two most damaged.

Fire Bolt
Twinned
Bolt #1: Ranged Spell Attack: 14 Damage: 9 (fire)
Bolt #2: Ranged Spell Attack: 11 Damage: 11 (fire)

Aiming carefully not to hit his compations, Xarroth takes out one of the ghouls ganging up on Lia. The second bolt misses the rest of the undead.

Initiative order:
18 Xarroth
17 Rhok (in melee with two ghouls)
12 Lothlién (10, in melee with two ghouls)
10 Five ghouls (9, -1d4 next save) (10)
  6 Lia (in melee with a ghoul)

Rhok goes next.

Rhok will attempt to take out the more damaged ghoul that's attacking him first, then will focus on the second

First attack with short sword:   Attack: 14 Damage: 6  

Colossus slayer:   8  

Second attack:  Attack: 24 Damage: 8

Lothlién casts Chill Touch again, on the most damaged ghoul in melee with him.

Attack: 14 Damage: 2 + disadvantage attacking me

Edit: rerolling damage with my last sorcery point (Empowered spell): 8

Rhok hacks at one of the ghouls on him, effectively taking it down. One of the undead atacking Lothlién shrieks in pain at the magical attack and the whole group of undead retaliate, trying to bite the people next to them.

Attack: 14 Damage: 7 against Lothlién.
Attack: 21 Damage: 8 against Lothlién.
Attack: 24 Damage: 7 against Rhok.
Attack: 8 Damage: 8 against Lia.

Since Rhok was bitten, he must succeed on a DC 10 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Initiative order:
18 Xarroth
17 Rhok (3, in melee with a ghoul)
12 Lothlién (10, in melee with two ghouls)
10 Four ghouls (9, Lia) (18, Lothlién)
  6 Lia (in melee with a ghoul)

Lia goes next.

Lia casts mind sliver again, targetting the one nearest her...

DC 14 int save. Damage is 6

Int save against mid sliver: -1

The ghoul in front of Lia clutches its head and wriggles in pain. It looks about to fall.

Initiative order:
18 Xarroth
17 Rhok (3, in melee with a ghoul)
12 Lothlién (10, in melee with two ghouls)
10 Four ghouls (19, -1d4 next save, Lia) (18, Lothlién)
  6 Lia (in melee with a ghoul)

Xarroth goes next.

Xarroth continues to sling fire at the relentless undead!

Fire Bolt
Twinned
Bolt #1: Ranged Spell Attack: 13 Damage: 8 (fire) 
Bolt #2: Ranged Spell Attack: 21 Damage: 10 (fire) 

Xarroth's fire takes out the most damaged undead fighting Lothlién, leaving the half-elf facing a single ghoul.

Initiative order:
18 Xarroth
17 Rhok (3, in melee with a ghoul)
12 Lothlién (10, in melee with a ghoul)
10 Four ghouls (19, -1d4 next save, Lia)
   6 Lia (in melee with a ghoul)

Rhok goes next, unless he is paralyzed as a result of post #1900.

Lothlién will use the same spell again on the ghoul in melee with him

Chill touch: Attack: 13 Damage: 9 + disadvantage attacking me