Apologies for the late reply!

A lot of stuff happened in my post, so let me try to break it down:
- Daemonspawn (fat man-sized Daemons) are regenerating right now
- Blightwing (flying Daemon Prince) is trying to shatter the 5 smaller crystals one by one
- The Steelheart (big metal-covered Daemon with a mace) is attacking a golem
- Several Cruelbeasts (roughly man-sized muscly Daemons) are attacking golems with maces/hammers
- The rest of the Cruelbeasts are closing in on Nethalika's flanks
- The Fire Daemon (huge winged red devil type thing) has breathed fire on Nethalika
- Soul Reaver is charging straight at Nethalika, psychically asking her what exactly she meant by saying she was planning to 'protect' this plane (he'd chat more leisurely but she's charging up a spell)

Phaerys' carefully timed attack had yielded results - while not destroyed outright, the central crystal had taken a good hit for sure. Another ring of smaller crystals were summoned to shield it from further harm, and that wasn't all they had to contend with.

From beneath his shelter of reshaped flooring, Phaerys observed the golems' arrival. Two near the now-ruined throne, and another pair near the door that he was closer to. That Nethalika was only now summoning reinforcements seemed to indicate that she may have underestimated them at first.

The upper surface of the shield he'd made was holding strong for now, but a concentrated attack from one of the siege golems would have made short work of it. He broke cover when bolts of darkness hammered the area, preferring mobility over getting crushed underfoot.

The Ataran raised his hands and concentrated on the nearest golem, forming a random arrangement of gravitic distortions in the area around it, sharply pushing and pulling this way and that in an effort to throw off its balance. For all the golem's size and raw might, it wouldn't be worth much without proper coordination. But due to the chaotic nature of Phaerys' little ploy, he was in no position to control exactly which direction it would blunder in.

The combined assaults of the Companions barrel towards their respective targets.  The beam from Blightwing collides with the targeted crystal, the dark object pulsing and exploding, unleashing a small shockwave of Darkness.  Kitharsis' spears slam into the remaining crystals, exploding brilliantly against the dark surfaces.  A moment later each of the crystals seem to flicker before exploding, unleashing a small pulse just like the first one.  At the same time Phaerys' plasma beam slams into the larger crystal.  As with the smaller ones it too seems to flicker slightly before unleashing a larger explosion of Darkness. However unlike the small ones it remains standing after the explosion, a shield once more surrounding it and 5 new crystals floating in the air.  Cracks are now visible however along the dark surface of the large crystal.

At the same time this is happening, the bullets unleashed by Vees guns scream through the air towards the Nethalikas even as Soul Reavers shockwave approaches from the other direction.  With all else going on the figures seem unable to properly defend themselves.  Knocked backwards by the shockwave they are practically propelled back into the spray of bullets.  Each figure cries out in pain, two of them seeming to almost liquify into a black shape before seeming to explode and flow back into the remaining Nethalika, the shockwave rolling through and obliterating the throne causing Vee to shift back to the other side of the room closer to the other Companions. 

The Shaiton seems a bit winded before she glances back at the crystal and scowls upon seeing the cracks.

"I must say Seraphim...your friends are certainly quite powerful.  We both know that were it just you and your ilk you could never have come this far.  She still has not returned.  Left you and yours to fend for yourselves like the vile betrayer that she is.  Accept the truth Seraphim.  He shall return momentarily and will embrace your kind and then we can do what needs done to protect this universe."

From under his helm, the Seraphims eyes flare up brightly as he flies through the air towards Nethalika.

"Liar!"

His hammer comes swinging down, slamming against a shield of Darkness forming around Nethalika as she holds her staff in front of her.  The two figures seem to struggle for a moment before in a pulse of both Darkness and Light the two are launched backwards a few steps.  Nethalika scowls at the group once more.

"Very well..."

She then gestures down towards the doorway and behind her to where the obliterated throne once was.  Two portals at each area appear (that's 4 total) and a Siege golem steps out of each one.

"Face the full power of Darkness!"

She slams her staff down into the ground and kneels down as a shield of Darkness appears around her and all can sense significant power flowing into her as she seems to start charging an attack.  At the same time the golems let out a screech as they move to attack the nearest Companion to them, unleashing clouds of toxin and bolts of Darkness.

Kitharsis follows quickly after Jharm as he rallies them behind him.  The Companions filter into the fort, finding no one to greet them until farther inside.

Someone beckons them further into the fort, whom Jharm confirms is Nethalika, a proficient wielder of the Darkness.  Kitharsis continues on, following Jharm deeper into the fort.  No doubt toward the room housing the crystal.

They are greeted by who he must presume is Nethalika, sitting on a throne.  Her fleshy wings unfurl as she stands.  She is perched in front of the Crystal, which is protected by a faint purple dome.  Kitharsis notes that the five floating crystals seem to power the dome. 

Dark purple smoke flows through the room and threatens to engulf them.  Meanwhile dark orbs scream down from above, targeting each of them.

The mass of sand building around him springs to life and raises above his head, shielding him from the orbs.

He sheathes his sword, while the three floating ones stay aloft.  Soul Reaver has released a shockwave to deflect the smoke, and Vee has begin firing a barrage at the backs of the three Nethalikas.

Kitharsis stretches out his arms to either side and summons long sandstone spears in the air around him.  Five in total.  They each glow a faint pulsing amber as they float in the air above him.  He pushes his palm forward, and the spears go streaking forward also.  Amber trails stream behind them as they pierce through the air.

Each one targets one of the five smaller floating crystals surrounding the larger one.  The spears are imbued with Kitharsis's pure energy, which should be quite effective against the Darkness.

Blightwing's spell is a potent daemonic attack spell with the potential to do a good amount of damage, but it's nothing like a Sphere of Annihilation or the like.  It would probably break through mid-range shields or defenses but powerful ones would block it.

Soul Reaver's Shockwave spell is very damaging to the environment and his foes and has a wide horizontal reach.  It won't hurt his allies - it'll like of just 'fizzle' around them if they end up in its path - but it could blast apart the stuff they're standing on (eg, the throne that Vee is currently perched on, if the Nethalika's aren't blocking the wave).

The Daemonspawn's defense against the orbs quite straightforwardly consist of them making sure they get hit instead of Soul Reaver by blocking them and tanking any of the damage they might inflict.  Their shields aren't magical, but Daemonspawn are very resilient.