Seeing the one Galvan hurting his little buddy Gorrah,  Chill switches his aim to that Galvan and maintains his steady aim.

Attack: 28 Damage: 32

As one of the Magen conjures a lighting bolt, Krom attempts to reduce the impact by interposing his shield. The dwarf parries both strikes of another Magen before swinging his flaming hammer in retaliation. The spectral dwarves continue their assault on all Magen within their reach.  

Action Warhammer attack on Demos C

Attack: 16 Damage: 10 +6 Fire damage 

bless 1

 Spirit guardians 16　Wis 15 on all Magen within range  

Reaction: Interception to reduce the first attack that hits Oli or Kazri by 3+4. Priority to Oli

@DM Krom thanks to the Mantle of Spell Resistance has advantage on saving throws against spells. I do not know if this applies to the lighting bolts cast by the Magen    

(@Krom, no it does not, they are not spells)

Wis saves DC 15 19 11 15 

Galvan A vs Gorrah

Attack: 7 Damage: 7

Attack: 20 Damage: 5

Galvan B vs Oli

Attack: 7 Damage: 10

Attack: 8 Damage: 5

Galvan C vs Kazri

Attack: 25 Damage: 10

Attack: 15 Damage: 5

Demos A vs Kazri

Attack: 21 Damage: 9

Attack: 19 Damage: 10

Demos B vs Krom

Attack: 13 Damage: 9

Attack: 16 Damage: 9

Demos C vs Krom

Attack: 17 Damage: 12

Attack: 6 Damage: 5

Gorrah takes a another shock from the shocking touch of the Galvan she is attacking as her friends and herself batter at it but it still stands.

The other Galvan also attempt to touch and shock their targets but the only one to hit is against Kazri (Krom cannot intercept, he is not within 5 feet of Oli or Kazri)

The Demos slash and cut with their greatswords but do not land hits.

Party back up

Chill (73/73)+3, Kazri (75/114), Krom (93/104), Rhogar (81/87), Gorrah (25/27), Oli (29/42)

Galvan Magen A (23/68), B (56/68), C (5/68) Demos Magen A (43/51), B (25/51), C (21/51)

Reaction: Investment of the Chain Master once more, halving the damage to Gorrah(-2 instead).

Once more, Rhogar and Gorrah's eyes light up just before the latter is struck, magically defusing, if not least reinforcing her natural resilience. Rhogar then scanned the battlefield, splitting his attention to see things from both Gorrah and his own perspective. "Hn. Change of plans." With a sharp tug at the space just above his brow, a mote of blue light appears at his finger tips, only to be flung away at Oli and soothe his aches upon contact. In the next moment, the dragonborn conjures more skeletal claws to rip and tear into the constructs' sides while Gorrah danced about in the air in such a way as to make her a harder target to hit. 

Bonus Action(Rhogar): Healing Light(2) on Oli, restoring 7 Hp. 

Action(Rhogar): Cast Twinned(1sp) (Cantrip)Reach of the End on Galvan(C) and Galvan(A).
(Lethal)Chill Touch - Attack: 3+18 Damage: 13 necrotic damage to Galvan(A).
(Lethal)Chill Touch - Attack: 1+16 Damage: 11 necrotic damage to Galvan(C).

Action(Gorrah): Take up Evasive Maneuvers. 

Kazri is slightly relieved that Oli was not hurt on this turn, then she sees that Rhogar took care of the minor wounds he had suffered previously. "Much appretiated Mr. Nimbatuul!" She determines that Oli should be able to finish off their previous target, so she will attack the next one. With a short prayer, Kazri's Dragon Slayer Sword gleams with astral radiance. (BA Branding Smite)

Kazri attacks Galvan Magen B

Sword Attack1: 19 Damage: 14 (+Bless 3)

Sword Attack2: 29 Damage: 10 (+Bless 2)

(Add 7 radiant damage on a hit)

Oli attacks Galvan Magen C

Beak Attack: 17 Piercing Damage: 5 (+Bless 3)

Claw Attack: 10 Slashing Damage: 13 (+Bless 4)

Chill watched the battle unfold and saw that the ones on the left,  the Galvan, looked to be being taken care of.  Seeing Krom beset by two demos but still holding his own Chill switches targets to aid him.

Steady aim crossbow attack vs Demos C

Attack: 15 Damage: 23

Krom easily deflects and blocks the Magen greatswords with his shield. "You will have to do better than this! This Firebeard is not going to fall against mere puppets!", shouts the dwarf as swings with all his strength the fiery hammer at the nearest Magen's midsection. The spectral dwarves continue their rentless assault on all the Magen within range.    

Action Warhammer attack on Demos C if it still alive, if not on B

Bless2      Warhammer Attack: 30 Damage: 12+ 4 Fire damage 

Spirit guardians 13　Wis 15     

Wis saves DC 15 9 6

Galvan A vs Gorrah

Attack: 11 Damage: 7

Attack: 16 Damage: 7

Galvan B vs Oli

Attack: 9 Damage: 10

Attack: 24 Damage: 9

Demos A vs Kazri

Attack: 24 Damage: 21

Attack: 17 Damage: 6

Demos B vs Krom

Attack: 20 Damage: 9

Attack: 18 Damage: 11

While healing Oli, Rhogar destroys Galvan C. Kazri lays into Galvan B with Oli helping out (C is dead). Chill takes a shot and destroys Demos C. Krom nearly destroys Demos B but both A & B still stand.

The battle continues to rage with Gorrah taking 3 (I figure Rhogar takes the same reaction). Oli takes 9, Kazri takes 21

Party back up

Chill (73/73)+3, Kazri (54/114), Krom (93/104), Rhogar (81/87), Gorrah (22/27), Oli (27/42)

Galvan Magen A (13/68), B (35/68), Demos Magen A (33/51), B (1/51)

Kazri clenches her teeth from Demos A's hit. "That was a good one." She thinks to herself, while pressing the attack on Galvan B. "You are doing good Oli, keep it up!"

Sword Attack1: 26 Damage: 10 (+Bless 4)

Sword Attack2: 29 Damage: 10 (+Bless 4)

Beak Attack: 16 Piercing Damage: 5 (+Bless 1)

Claw Attack: 11 Slashing Damage: 11 (+Bless 3)

Krom gives a nod of appreciation at Chill as the tabaxi finishes off one of the Magen. Noticing that one of the Demos is barely standing, Krom strikes the other one with his fiery hammer, sure that the spectral dwarves will take care of it. The dwarf moves closer to Kazri in order to protect her and at the same time to allow the spectral dwarves to also attack the other Magen.

Action Warhammer attack on Demos A

Bless 4  Warhammer Attack: 26 Damage: 12 + 5 of Fire damage 

Movement : 5ft to the left (if I read the map correctly it should put me next to Kazri/Oli while remaining within range of Demos B and allow the Spirit guardians to also reach one or two Galvan)

Spirit guardians 16 Wis 15 on all Magen within range 

Reaction (if applicable) to reduce the damage on Kazri or Oli (priority Oli) by 1 +4            

Sensing an end to the battle being eminent, especially in the wake of his companions press of attacks, Rhogar relents on encouraging a more defensive posture. Instead, twice over he unleashes his will as deadly condensed orbs of arcane force, before bidding Gorrah to do much the same in a biting the same target, if not another nearby construct.  

Action(Rhogar): Cast (Cantrip)Force of Will on Galvan(C) and Galvan(A).
(Lethal)Eldritch Blast - Attack #1: 4+24 Damage: 8 force damage to Galvan(A).
(Lethal)Eldritch Blast - Attack #2: 4+12 Damage: 8 force damage to Galvan(A).

Bonus Action(Rhogar): Command Gorrah to Strike again!

Action(Gorrah): Hell Gnaw vs Galvan(A).
(Melee, Lethal)Bite - Attack: 8 Damage: 6 magical piercing.

Chill fires at whatever foe is left over.

Attack: 17 Damage: 30

The onslaught is complete.  Oli lands the finishing blow on Galvan B.  Krom and Rhogar weaken their targets, Chill finishes one Magen off.  The spiritual guardians finish off the rest.

Combat over.  All foes have disappeared in a burst of harmless fire and a cloud of smoke that quickly dissipates. All that is left is the chainmail and greatswords of the Demos.  The others leave clothing but nothing else of value.

"Hopefully those were the only Magen guarding this building. I'm not eager to find out what kind of abilities and powers the robed Magen may have." says Krom after the spectral dwarves finish off the constructs. The dwarf pats Oli's head as he walks closer to Kazri. "That lightning bolt hit you badly, lass. Eat this, save your powers for later, I think we are going to need your Smiting powers later." Krom gives Kazri the enchanted purple pear. "Speaking of smiting, I've noticed you haven't channeled your holy powers into your sword recently. Is this a deliberate choice or is it somehow linked to influence of this place you were talking about earlier?"

OOC
@Kazri - By eating that pear you heal 3d8+3 (cure wounds at 3rd level)

Chill rejoins the others as they stand in front of the tower.   He looks up at the tower and gets his measure before moving to the door.

"For a dead city that fell thousands of years ago this place has quite a few tricks left in it.  The Netherese must have been pretty powerful mages for some of this stuff to still work."

He looks the door over for moment and then turns back to the others.  

"Let me check this throughly before we proceed.  Those were quite the guards just for an observation tower."

Chill then gives the entrance and door a thorough look to make sure there are no traps or other surprises. 

Investigation 20

Chill inspects the door.  He doesn't find any traps.  What he does find is that the iron door at the base of the observatory is welded shut from the outside and must be broken down if you want to enter.