(Also, should I have rolled initiative for the mount? Or will she just go on my own for simplicity's sake?)

She ll go on your own 

Initiative 19

Perception 18

(Sweet deal. Also, how far away are we from the creature? Or is all that and more being covered in one big post?)

The creature is moving in front of the sobbing dark elf clacking its mandibules.

It is 40 feet from you and 60 feet from the other entrance farther to the east. The elf is 50 feet from you and back to the wall. 

None in the room have noticed you yet. 

Spoiler for our mage only. 

As the others took up more tactical positions or attacked, Nym will forgo an immediate attack oh his own to instead mount up onto Lokk. "Again and again and again, he slipped from her grasp. To hesitate meant death. To stop meant a fate worse. All would later know the true meaning of swiftness after that day." He solemnly intones during the process. As if in response to the quoted passage, the invisibility fades to reveal  not only Nym in his true form, but also a distorted air both beast and elf. Even the slightest movement from the pair left an after image.

At but a mental prodding from her rider, Lokk would TRY to scrabble up to the priestess (sidestepping the spider if possible w/o OA), and grab hold of the priestess in her mouth. If not at the very least get within range to do so in the 1st real round. 

(OOC: Turn order is Aryil, Cyrhan, Nym, Try'gan. I'll enter my action once Aryil has entered his)

Aryil moves out and across the cavern, positioning himself where he could attack either of the targets with a small amount of movement, he sheaths his hand crossbow and readies his second dagger. 

Cyrhan will move toward the side of the Aranae, mindful of any web, and he will cast wrathful smite on the creature.

(OoC 2 Attacks, first one with advantage. If it hits, wis save vs 17 or frightened and speed =0, only once, not on both attacks!)

Attack 29

Attack 26 

Wrathful Smite Damage: 17

Regular Damage 7

Edit: Assuming both hits, I've added the damage for the attacks.

The others can do their moves.

Aranea will act next round at 14.

(Sorry guys got fingers of my right hand that are still very much damaged so takes ages to write. I ll do short posts but I m here.)

(Think its only Tyrgram at this point, and understood good sir.)

"Do not believe that ***** " he says to the others while starting waving his hands " she is not crying at all...she is pretending"

With that a little fireball flies across the room and past the two figures and explodes in a massive fireball that engulfs both the elf and the spider, but just scorching Cyrhan eyelids.

"Good. All the more reason not to be gentle about her capture!" Nym calls out as he took off to carry out the snatch and grab (mentioned in#227). 

(Forgot to post this last, but for the lizard's grapple attempt on the priestess: Strength Check: 20)

(Ya failed me yet again Lokk!)

For DM: 

Keeping his attention to the creature, leaving the more important prey to his mate, Cyrhan just says, with surprise and innocence that is perfectly out of place here:

"But... I'm never gentle!"

Quote from Orileo >>

 

For DM: 

Should I have also rolled Lokk's HP, or just go w/ the average?

 Average is fine 

The fireball exploded and thanks to Tyrgram warning no one is blinded by the harsh and sudden light. 

Both, aranea and the sobbing drow are engulfed. They scream in unison and the drow begins shifting into the form of an aranea. Though they are badly hurt they are still standing. 

For Tyrgram

“There are more down there! “ warn the wizard to his comrades “At least one priestess...” 

( It’s now our first turn in initiative order isn’t it? ) 

Yes it is. 

The Araneas will move at 14 and the other drowns will be you don't know. 

Yes it is. 

The Araneas will move at 14 and the drows you don't know yet. 

It is up to you now

OoC: I'll let Ayril go. Just let me know if the drow reported by Trygan move before me, as it might  change my action (I'd be in their way, right ?).