Oh well...

Stealth: 9; Perception: 7.

Thelanis begins to step down the ladder lower into the depths. She hears some jeering and growling coming from down there. But one of the beams on the ladder breaks about halfway down. Some of the jeering stops and she hears someone say something in goblinoids. Then a couple of footsteps coming towards the ladder.

Valar closes the lantern and steps away from the lip. 

Thelanis has 120 ft darkvision with Devil's Sight. Can she see what's going on below?

"Looks like battle." whispers Draíocht. "Let them get up the ladder first?"

He takes position behind cover, if it exists, and knocks an arrow in preparation for goblins coming up.

Valar will move back to where he can find a suitable, concealed position. 

Amiz watches from the top of the ladder ready to get out of the way if Thelanis scrambles to the top of the ladder or in case he needs to jump down to assist them. 

Thelanis rolled quite poorly on her Perception check. So all you could ascertain was growling and jeering noises, and then footsteps towards the ladder after the ring broke. Is Thelanis heading back towards the storeroom?

Also anyone attempting to hide in here will need to roll a Stealth check.

Valar stealth check: 8

Amiz does not choose to be stealthy and stands firm ready to join the fray if combat break out. 

Draíocht Stealth: 17+3 = 20

Draíocht blends into the shadows of the storeroom while Amiz stands firm. Valar attempts to hide as well, but is more visible with the lantern in hand.

I just need to know what Thelanis is doing. Coming back up the ladder I assume, but what then?

Thelanis climbs back up and walks a few feet from the ladder and turns around, facing the ladder.

She readies an Eldritch Blast to strike anything climbing up the ladder.. [[AC 24; 10 force damage]]

After a few moments. You hear people coming up the ladder. As they reach the top, you see a hobgoblin stuck their head inquisitively into the storeroom. It looks at first surprised, and then incredibly angry to see you all there. Here’s initiative:

Group 1: Thelanis, Amiz, Valar

Group 2: Hobgoblins

Group 3: Draíocht

Thelnis, Amiz, and Valar are up. The first of two hobgoblins have reached the top of the ladder and have spotted you all.

Valar attacks, attempting to strike hard enough to drive the hobgoblin down onto the others coming up the ladder. Attack: 18;/ damage: 14

The angry look on the hobgoblins face turns to fear in the realisation that he can do nothing to stop Valar’s sword from slamming into its face. It’s body falls onto its friend below who lets out a scream as he tumbles down the ladder with it. Taking 3 falling damage.

The sounds below change as the rest of the hobgoblins shout some things in goblinoid. I forgot, can anyone speak goblin?

Amiz does not speak goblin. He attacks the other hobgoblin 

battleaxe

25 (crit) to hit and 18 slashing damage - rolled in game log

Thelanis releases her readied action from above.   [[Eldritch Blast AC 24; 10 force damage]]

[[If her readied action occurs before initiative and she gets another attack, it's an eldritch blast AC 21, 9 Damage.]]

Amiz are you going to go down the ladder into the next room to attack the hobgoblin that fell down the ladder? You’d get advantage because it is prone. But this room hasn’t been scouted yet, so I thought I’d just let you know that before you rush in.