"Oh, don't you remember, Katryl?" Khessa answers "One of the last things we discovered about Ogremoch's Bane was that Dispel Evil and Good was needed to get rid of it once and for all. And such wondrous magic should now be available to our dear Lulu! That fool cloudy annoyance will be taken care of in no time!"

"Ahhh," Katryl replies to Khessa. "Guess I've not paid that much attention to all that magic stuff. We just need to go cast the spell? Shouldn't we do it now so they can try to get as many elementals as they can?"

"That's the spirit, my friend!" Khessa enthusiastically pats Katryl on the shoulder in agreement. "It just depends on whether Lulu has already prepared the spell we need or if she needs a few time to do it" she turns to the holy firbolg, waiting for her response.

"I'll need to rest before I can channel magics of that level again, but we can certainly see it done on the 'morrow," Lulu nods. 

Then unless anyone has some particular they wanted to do that day it is easy enough to head back into the caverns to dispel Ogremoch's Bane. While you are out taking care of that lingering business, the rest of your allies arrive at Blingdenstone, though rather tired from a hurried march.

Khessa is happy to see all her allies again and hugs them with enthusiasm. She is also very pleased to see the holy firbolg get rid of the perverse creature that had seemed unbeatable to the party that first arrived. "And may it happen the same to those planar wastes known as 'Demon Lords'!"

In the days in which the small 'elite group' of elementals is summoned, the blonde arcane warrior trains with renewed vigor and commitment, knowing full well that the fate of the mortal dimension is at stake. If the members of the army, once they have learned the nature of the final enemy and 'enlightened' by Traydark on the risks they will run, decide to participate anyway, she involves them in the training and tries more than ever to bring out the best in them - accustoming them to keep themselves in the background and to strike without drawing too much attention to themselves.

When the time comes to leave, the tall adventuress is as ready as a mortal can be to face a legendary incarnation of mad eternal evil. '...All in all, in the end, when there is only one left to beat, he will certainly be terrifyingly powerfull... but he will be alone. He will fight only for himself. For the pleasure of spreading death and destruction. For his power. For his pride. Maybe even just for his whim. I, though infinitely less powerful...' she thinks of her family, who deserves to finally live in peace and freedom... of Traydark... of the party and army members... of the Diggermattocks and the innocents of Blindgenstone... of Zhora and Hanne and the innocents (however few they may be) of Menzoberranzan... of the Stonespeakers of Gravenhollow... of Thamiel, the petrified fallen Angel whom perhaps one day she will be able to help... of Dawn, who does not deserve to lie forgotten in the darkness of the Underdark again... of Globbagool, the Ooze hero, whose sacrifice must not have been in vain... '...I am not alone. I have so many reasons to win... So, better prepare yourselves, Demon Lords... break time is over!'

Horkas trains hard, working new combinations and moves with his constructs. On one day, between her other duties, the artificer approaches Lulu and asks her to store a spell in the shield guardian. He recommends Spirit Guardians, describing the awesome potential of a large metal blender wading into melee with a demon army...

Katryl of course volunteers to accompany Lulu when she goes to dispel Ogremoch's Bane. Otherwise, she really doesn't have much to do for herself to prepare.  

She does however try to find time to speak with Lulu in private and is often talking to her: 

Lulu is glad to help however she can with the dispelling of the evil cloud. After, she falls into much the same routine as usual, cooking when she can for their group. Singing when the silence feels too heavy. And training when her thoughts turn dark. She also works alongside the deep gnomes to gather herbs for healing concoctions whenever she can. 

It's during the latter that Horkas finds her, and she's quick to pause her task in lieu of whatever her dear friend needs. She laughs at the picture his words conjure and, indeed, stores the divine magics for the spell into the Guardian. "There. A metal blender," she says, patting the large construct's chest. "If all went as it should, they should manifest as wee mechanical pixies wielding blending blades."  

The reuniting with their wayward allies does little to dispel the dour mood of the noble drow, and when it is time to bring up the plans ahead he would not hold back when describing the horror at Sloobludop, making it very clear what they would be up against, and that was only one of the many demon lords known to defile and corrupt the Underdark. While there was no doubt dying in battle to protect the realms would be a noble cause they would need to at least stand their ground or they would be a liability rather than an asset in the battle to come.
That said he makes no further attempt to dissuade anyone to give their lives in what he believes is a futile effort to help. As for being more constructive he would offer to organize the elementals, something he had some experience with after all, and them being entities that would likely not flee and most likely could have an actual impact on the battle he felt comfortable with having them brought into the final stand.

Persusion if applicable to dissuade allies from needlessly sacrifice their lives and endanger the mission: 25 + Dark One's Luck: 10

None of your allies are overly set on throwing themselves into a mindless melee with the demon lords. They are quite content to assist you all in whatever your plans might be. They are supportive of using a less occupied space as to lessen potential casualties.

How long do you stay in Blingdenstone before leaving?

Khessa was prepared to 'spend' up to a week, to allow Blindgenstone's forces to summon the Elementals to help.

Horkas and the constructs are ready to leave as soon as possible. "No point delaying the inevitable!" he would exclaim with enthusiasm. "What will come will come - at least we will be doing something positive to end this curse!"

As soon as the week is complete and as many elementals have been gathered, Katryl is ready to go.  

With Lulu: 

Lulu, too, is ready whenever the others are to bring the grimoire back to Vizeran and to make their way to the site of their final confrontation. She'll give both Khessa and Katryl a potion of healing to keep for emergencies. 

When they're sure the next day will be The Day, the cleric will perform a ceremony of Dedication for Katryl, further tethering her to the Mistress of Moonlight's protection.

Traydark would be ready to leave as soon as the others are, spending his time in solitude in the adamantine tower, brooding over his life and the battle ahead.

By the end of the week there are 6 elementals summoned, each with a deep gnome standing by to lend their assistance in controlling them, noting that if the elementals are destroyed they won't be able to bring them back. But they vow to stay in relative safety as much as possible.

On the way to the troglodyte lair you can let Vizeran know you are on your way to plant the heart since it will take him some time to cast the ritual (9 hours in fact). But arriving eventually at the lair you have plenty of time still to arrange yourselves and make ready for the final act.

It is eerily quiet in the spacious lair and still reeks of its former occupants.

Khessa lets to who has chosen this battlefield to place the Heart where they think there is the greatest tactical advantage to gain... and instructs the Elementals to hide in the earth near that spot, out of trouble, ready to emerge as soon as the Royal Rumble is over and only the last Demon Lord remains.

After that, the blonde arcane warrior hides with the other party members, awaiting the final showdown. She waits to cast preparatory spells, since the Royal Rumble could last a long time... she will cast the preparatory spells as soon as only the last Demon Lord remains.

The noble drow too would stay out of sight and await the endgame when he would make his own preparations.

"I'm ready to follow whatever plan you all decide on," Katryl says. "Horkas? I think perhaps you and Lulu were in favor of this spot? Where shall we set things up?"