WIS save: 20

Belthomias feel disoriented and find himself close to Vishnu. Regaining his focus, he assess the situation and nods at the rogue.
The ranger runs at full speed toward the creature (AS50 > AS38) and disappears surrounded by silvery mist, to reappear instantaneously in close proximity with the Seer (AN-32).
"My name is Belthomias, you killed my people. Prepare to die..."

Belthomias is ready to strike if the Seer moves away

Seeing that the seer has finally changed targets, Quadere takes the chance to go on the offensive, moving to AS-43 and sending a searing bolt of light across the chamber while her spiritual weapon moves to close the distance. 

Guiding Bolt: Attack: 22 Damage: 15

Vishnu will release her attack, assuming Belthomias is within 5 feet.

(Should have specified that or if sneak attack was applicable otherwise, could have gotten it from the advantage.)

WIS Save: 2

 Kandalou will get to the seer (using his movement and Misty Step racial ability. If he can't make it there then I guess he will just take a dodge action.)

If he can make it:

-> Longsword, +1 vs. Seer: Attack: 24 Damage: 12

-> Longsword, +1 vs. Seer: Attack: 11 Damage: 13

Using his reaction for the Protection style, imposing disadvantage on anyone the seer attacks within 5ft.

(@Superbad: As you described, Kandalou cannot quite make it to the Seer this turn.)

Belthomias quickly nullifies the Seer's trick with a combination of running and teleporting. Though he doesn't attack immediately, he does find the time to threaten his foe.

Kandalou likes what he sees and also uses a combination of moving and teleporting to get closer to the Seer {AO-38}, but decides to take a more cautious approach.

Vishnu takes advantage of Belthomias sudden approach and releases her arrow at the distracted Seer. As usual, her aim is as accurate as they come, and the creature's shoulder shall never be the same. (Seer takes 31 magical piercing damage.)

Quadere also goes on the offensive. Both cleric and spiritual weapon move closer to the Seer, with the former launching a streak of light at her target. She hits the other shoulder, leaving it shimmering in Oghma's light despite the room being quite well lit already. (Seer takes 15 radiant damage.)

(Ulitahrid goes next.)

The Ulitharid [Tooltip Not Found] more energy into the Gith Capacitor. The light it emanates now also pulsates. Surely, the tentacled aberration is almost done charging its artifact.

END OF INITIATIVE ROUND 8

THE FAR REALM - INITIATIVE ROUND 9

• 19. Vishnu (51/66) - 
• 14. Seer -  next attack against it has advantage;
• 11. Belthomias (66/85+15) - Potion of Psychic Resistance, Aid;
• 11. Kalak (0/38)  
• 11. Kandalou (90/94+15) - dodge, Aid;
• 10. Quadere (18/66) - Light, Spiritual Weapon (counter: 7); 
• 09. Mind Flayer 
• 05. Shai (0/66+15)   
• 04. Ulitharid - 
• 04. Hulk 

MAP:

 

NOTES: Everyone should begin each of their turns by rolling a WIS saving throw {DC 7}. If you fail this check, you'll also need to roll a d10. Also, the map should be self-explanatory following my description above, but let me know if you have any clarifying questions.

(Vishnu is up next.)

Wis save: 6

(Ffs)

4

(@Shadow: Vishnu doesn't move or take actions this turn.)

Vishnu sees another chance to shoot an arrow at the distracted Seer, but has to pause to refocus her mind for the next few seconds.

(Seer goes next.)

DM's Screen:

The Seer is visually dissatisfied with how quickly Belthomias was able to approach it again. It brings its horrid staff up and then down on the gith's head twice:

-> Comet Staff vs. Belthomias: Attack: 17 Damage: 31 bludgeoning and psychic.

-> Comet Staff vs. Belthomias: Attack: 23 Damage: 24 bludgeoning and psychic.

The ranger blocks the first wack with his glaive, but not the second. (Belthomias takes 19 bludgeoning and psychic damage.)

(Belthomias, Kandalou, and Quadere are up next. The first attack against the Seer has advantage.)

WIS save: 8

(It was a total of 8.... something weird happen when I added the attack rolls and I cannot find out what... I'll just post a fresh roll under if that ok)

Belthomias focuses on his enemy and drives his magical strength into his glaive (Planar Warrior skill, bonus action) and strikes.
Glaive 1st attack: 9, magical damage 13
Glaive 2nd attack: 13,  magical damage 6

If one attack hit, it becomes Force damage and add 8 force damage

(I'm not sure if there's an advantage due to the guiding bolt, but here's another roll in case: 26)
CRITIC !!!!! Add another 3 !
(reallly...1 ?) :(

WIS Save: 14

Kandalou will finish his movement toward the Seer and will give him the wombo combo with is longsword.

-> Longsword, +1 vs. Seer: Attack: 29 Damage: 17

-> Longsword, +1 vs. Seer: Attack: 26 Damage: 10

Will use his reaction to use the Protection fighting style.

Second attack crits: 7

((SECOND CRIT WHERE I ROLL A 1!!! ARRRGGHHHHH))

Quadere leans into the assault, whacking the seer with her spiritual weapon before adding another Guiding Bolt into the mix, hoping to give Vishnu another opening.

Spiritual Weapon: Attack: 14 Damage: 5 Force

Guiding Bolt: Attack: 21 Damage: 7 Radiant

Edit: Forgot the Wisdom save, not that I can fail it...

25

For a moment, Belthomias channels some extraplanar energy into his glaive and slices the Seer. By the time his weapon swings around for a follow up attack, it has already returned to its normal state. Quadere's previous strike makes it a bit easier for the ranger. (Seer takes 21 magical slashing and force damage.)

Kandalou arrives to confront the Seer as well {AO-32}. He adds to the hurt with another two swipes of his blade. (Seer takes 17 magical slashing damage.)

The Seer is visible weaker now.

Quadere sees the Seer is weakening and adds to the assault. First, her spiritual weapon wacks the Seer one more time. Then, she tries to follow that up with another guiding bolt, but her aim is a bit off. (Seer takes 7 force damage.)

At this point, the initial crack in the energy barrier isolating the Ulitharid becomes wider. It multiplies into a multitude of other cracks as the energy somehow remains swirling. The Ulitharid looks worried, but it is too close to its goal to focus on anything else.

(Ulitharid goes next.)

The Ulitharid is close, and it knows it. It [Tooltip Not Found] more Far Realm energy into the Gith Capacitor and its long face tentacles begin vibrating with the anticipation of completing its tasks. The pulsating light from a moment ago now strobes intensely. If the Ulitharid gets a chance to charge the artifact one more time, there is little doubt it'll succeed in its mission.

END OF INITIATIVE ROUND 9

THE FAR REALM - INITIATIVE ROUND 10

• 19. Vishnu (51/66) - 
• 14. Seer - has some half cover from ranged attacks from being basically surrounded;
• 11. Belthomias (47/85+15) - Potion of Psychic Resistance, Aid;
• 11. Kalak (0/38)  
• 11. Kandalou (90/94+15) - Aid;
• 10. Quadere (18/66) - Light, Spiritual Weapon (counter: 6); 
• 09. Mind Flayer 
• 05. Shai (0/66+15)   
• 04. Ulitharid - 
• 04. Hulk 

MAP:

 

NOTES: Everyone should begin each of their turns by rolling a WIS saving throw {DC 7}. If you fail this check, you'll also need to roll a d10. Also, the map should be self-explanatory following my description above, but let me know if you have any clarifying questions.

(Vishnu is up next.)

Wis save: 5