Nodjeim take a moment to go over what he is doing in his head, and then does it.  Stepping up (and towards the foe if need be for range) Nodjeim lights one of the devices he's fashioned and throws it towards the most southwest foe near the cages...

Improvised Device Attack:  19 on a straight die roll.  +7 is Nodjeims modifier for daggers, darts, handaxes, etc... Modify as you feel right? For, I believe, 5 fire damage for each turn it is on fire or in the area of the fire?

     "Finish him off," Nodjeim calls out to those near him (Chakka and Threlan?) Any movement Nodjeim has left would be spent heading Northeast wanting to use the other such device someplace more central to hopefully be a bigger distraction to the other foes... (50ft movement total available to him.)

Threla immediately sees the undead see the chicken and then pounce on it. They look confused when their rotting paws pass straight through it. With a nat 20, the leftmost guard notices and approaches the chicken. As it leaves the other behind, Veldruk and Olan move in, striking at the remaining guard. It stays up, but looks badly hurt. 

Meanwhile, Nodjeim tosses the firebomb at the gnoll guarding the hyenas, and it goes up in flame. Ruthmum, now able to see the gnoll, conjures up a flame and tosses it at it. He rolls two natural ones even with advantage, and the flame goes wide... impacting the cage holding the giant hyenas and lighting it. Furthermore, the flames from the hyena master lick against the cage, catching even more flames. Chakka rushes in and slashes at the gnoll, digging into it twice. It survives, but from above, you hear mighty wingbeats. Those with darkvision can see a giant vulture approaching from above, talons outstretched at the gnoll.

Evelyn and Threla, you both still have combat actions that you can take in the surprise round.

After the surprise round, Threla, Evelyn, Olan, Nodjeim, and Veldruk may all go, since I rolled crazy good initiative for you.

The current situation:

Oh ho ho!

Threla waves her hand, and flickering multi-hued flames burst in an explosion around the big group if enemies around the top right wagon, as she casts faerie fire. All of them must make a DC 14 Dex Save or any attack roll against an affected creature or object has advantage if the attacker can see it, and the affected creature or object can't benefit from being invisible and for the duration, objects and affected creatures shed dim light in a 10-foot radius.

With her bonus action, she gives a Bardic Inspiration (+1d6 to next d20 roll) to Olan. "Fear us! For we are from the shadows!" [Intimidation, just for dramatic affect: 13]

Evelyn moves so that she can see the gnoll Chakka is attacking. It looks almost dead so she quickly casts some more Fire Boltfire at it to finish it off. Then she retreats back to her position in cover.

Attack: 21 Damage: 2

OOC: Yay! I get to go again. But before anyone acts, we should resolve the effects of the faerie fire spell, since that gives advantage on attacks.

All but one witherling fails the saving throw.

Threla, Olan is not within 60 feet of you, so you can't give him bardic inspiration. Additionally, shouting seems like a pretty bad idea right now. So far, nobody has actually shouted out, since no gnolls' turns have passed, though the fire will very soon spread on the cages and it can be assumed that the hyenas will begin making noise when it spreads.

If the gnoll at the entrance is still standing, Olan will try to finish it off. If not, he'll switch to whichever target is nearest.

Attack 22

Damage 9 (4+5)

     Nodjeim, with his 50' of movement, is heading Northeast from his current position (shifting a bit to around the cage) to try to get into melee with those affected by the Faery Fire. I believe he can get into position to attack one of the gnolls?

Unarmed Strike Attack:  11 to hit for 10 bludgeoning damage
BA Unarmed Strike Attack:  14 to hit for 9 bludgeoning damage...

Olan sticks an arrow into the gnoll's neck, killing it, while Nodjeim goes to town on the remaining living gnoll that isn't on fire (the one on fire has fewer than 5 hit points, and will die on its turn). It survives, but just barely.

Threla, Evelyn, Veldruk, you're all up!

Oh, also, forgot to post initiative order:

First: Literally the entire party, Ruthmum and his Vulture

Second: Gnolls and Witherlings

Third: Chakka

Fourth: Zombies

On that note, actually, Ruthmum and his Vulture will take their actions, the gnoll's gonna burn to death so the vulture just spends its turn heading after the other gnolls, and Ruthmum uses druidcraft to snuff out the fire on the cage.

Oh yeah, huh. So, Threla does not shout, and if its fine, would give the bardic inspire to Nodjeim, both for an attack roll or if Evelyn decides to drop a [spell[thunderwave[/spell] on those fools.

With a bonus action, she seeds doubt in the mind of the most dangerous looking living gnoll within 60ft of her, using Unsettling Words, and then, with a wave of her hand, she whispers in the mind of the gnoll, casting dissonant whispers on it. The gnoll must make a DC 14 Wisdom Save, with a minus 5 penalty, or take 16 psychic damage and must immediately use its reaction to move as far as its speed allows away from me.

(I do that a thunderwave would actually be the worst possible decision here, but you're free to make whatever decision you like, I'm not your boss.)

The gnoll absolutely fails, and runs through the gaggle of undead away from Nodjeim, provoking an opportunity attack.

Time and experience had taught him to expect the worse, only and always. It was a surprise and a welcome one, to see a single guard remaining in front of the cave after fire and illusion.  Carried on ghost wings, he said with the voice of his mind as a new arrow felled the sentinel. The drow turned towards his companions fighting below, repositioning himself so he could hit one of the undead from beyond its darkvision. He raised the sword arm, pondering how it was almost comic to see that the gnolls had tried to use shadows to their favor. Ignorant monsters, wandered into his territory without knowing, made themselves all but easy targets that couldn’t even see where he stood.

A simple whisper, a simple word, arcane yet familiar, and the blade fell. Once again, a beam of crackling energy flowed from steel, seeking a skeleton. It was almost like throwing the cut from the blade, ignoring its natural limitation of range. The power was nothing that impressive, Veldruk knew. To the point that part of him could not help but regret not focusing more on Eldritch Blast. Maybe I should abandon the Devil’s Sight. It was something he took only to remediate his sunlight sensibility, after all.

Notes: Veldruk repositions in a way that he can target a sekeleton bellow from outside said sentinel's darkvision. He then uses his action to cast Eldritch Blast (21 to hit, 2 force damage).

(Important edit: I forgot that dissonant whispers also deals a shitton of damage. The gnoll just straight up drops dead from that. The only foes remaining are the undead, which can be wiped out pretty easily using ranged attacks, and they don't actually make any noise.) 

The last living gnoll falls, and the rangers of the group easily slay the undead from a distance. Out of initiative!

OOC: Goodness. That was easier than expected. To be clear, the hyenas are still in their cages, correct?

Threla dusts herself off, sheathing her rapier. She gathers her companions, along with their new Druidic Friend and his Bird. "Well, that was not much of a resistance. I would say our plan worked quite well. What is our next course of action? If I had to guess, there will be more of those fiends in that cave" She points to the cave mouth "I am not hurt, and everyone else does not appear to be, but I am feeling my creativity ebb and flow, I may need some time. Of course, we could keep this momentum going and continue on!"

OOC: Essentially, Threla's  limited pool of magic is represented by her creativity and passion. When she runs out of spell slots, she has a 'burnout' so to speak

((Evelyn is also out of spell slots.))

"I am at the limits of my magic for the moment as well," Evelyn agrees. "Yet it would take too long to stop and rest. We should press our advantage while we can."

The wizard finds the encroaching darkness unsettling but tries not to show it. Among her peers at the academy she hadn't had much cause to regret the lack of darkvision, but now she wishes one of her parents had been an elf.

"Th' gnolls are sure t' replace their watch eventually, and then they'll certainly be on high alert. If we're itchin' t' kill 'em in the best possible circumstances, these are those."

The undead made for the perfect enemies in that situation – silent and frail. It took little effort to dispatch them, little time, and the two groups become one again. It was far from comfortable to know that two of their casters had spent their forces but he had to agree that they wouldn’t have a better opportunity to clean that den of monsters.

“We should keep watch to the entrance of the cave and finish the hyenas.” Their noses would be a problem if they had to retreat. Not to mention that through numbers alone they were a danger to fight. “From there, unless we get enough material to block the cave entrance, our best bet will be going in.” The warlock looked to the bard then to the place were the rogue killed the first sentinel. “Between me and Threla we should be able to see the gnolls before they see us.”

In saying that Veldruk turned his eyes to the cavern. If the enemy base was divided in different areas it would be possible to trim their numbers two or three monsters at time. The stronger ones should be deeper inside. What if they are a single area? Asked the voice of his mind, imagining the worst-case scenario.