The skeletal horse seems driven by a desire to pummel Nirzeg to death. It attempts to trample him as soon as Nirzeg gets near. 

Attack: 11 Damage: 9

// You can make an opposed Strength (Athletics) or Dexterity (Acrobatics) check, if you wish to attempt to mount the horse. //

"Not. Good enough!" Nirzeg he says, deflecting the hooves as he ropes around to try and leap atop the skeletal horses back. "C'mon now. Obey." He commands as he tries to go to reel it in by the reins.

Athletics: 11.

Opposed Str: 18

Nirzeg is able to hop into the horse’s saddle. The undead creature immediately starts trying to throw him, bucking and rearing, then takes off at a full gallop towards the Hunt Lords’ Keep! 

The Aarakocra man kisses his fingers as he watches the wight and its horse get dusted by the combined efforts of Genny and Astra. "Ah, perfecto."

He summons Sparky over to him. The bird lands on his arm. "My dear, I think it best we clean up the mess we've made, yes?" He extends his arm and Sparky begins circling the forest fire they created with the Fireball, as the Aarakocra repeatedly casts Control Flames, extinguishing another five foot cube of fire every six seconds, working from the outside in. As Sparky goes to work, and as the Aarakocra continues to trace the Control Flames sigil again and again, he turns to address the others, just as Nirzeg zooms by on the back of the remaining skeletal horse.

"Oh, ah, adios, then!" he shouts towards Nirzeg. Then, to the others "He is rather bold, yes? You all are, really--out here fighting these ugly things as the sun sets. Quite romantic, such passion and fervor."

He smiles and waits a beat. "Oh, but of course. Introductions are in order." He bows deeply and formally, his right wing folding along with his right arm in front of his chest, his left wing and arm outstretched fully to the side.

"Ah'brasar, agent of the Emerald Enclave, Caretaker of the Star Mounts, at your service, friends." He rights himself, acknowledging the confused looks he is receiving. "Our organization is very good at...how you say...thinking ahead, you see. We had senses that one of our agents may be in some peril, and so was asked to take up his post and join his allies on their quest. And if I am not mistaken..." he points at the Dragonborn, "the loyal Sir Derrikoth," then at the Aasimar, "the bold Lady Astra," then the Warforged "the charming XJ9 unit, or shall I say, Miss Genevieve," then he looks off in the distance, "and I can only assume the crazy one trying to ride that demon horse is the brilliant Mister Nirzeg, yes?"

"May I be so bold as to ask what fate befell our friend Alus, Cleric of Valkur, and fellow agent of the Enclave?"

Astra smiles as the rather interesting Aarakocra puts out the flames introduces himself to everyone. And he even knew who they were too! But her smile vanishes when he asks what happened to Alus. "I'm afraid that he was killed a little over an hour ago. We had actually just finished burying him right here and paying our respects when those monsters attacked us."

 "I am so very sorry for your loss." He grabs Asra's hands. "I knew not this Alus, but was told he was a special soul. The Enclave will suffer in his absence, ciertamente." He then gestures to the fresh mound where Alus was laid to rest. "May I?"

Astra nods and looks towards the rest of the party to see if they're going to give approval as well.

Assuming he gets the go ahead from Genny and Derri, he will walk over to Alus' burial site and kneel. He will gather some twigs and brush from the surrounding area and pile them atop the mound of dirt, and will shoot a [Tooltip Not Found] into the center of the pile. He will then use Control Flames to increase the width of the flame, to change its color to blue, and then to animate the flames into the shape of an Elven man.

"Alus, agent of the Emerald Enclave, acolyte of Valkur, please, be at peace." He uses Control Flames to later the shape of the fire once more into a crashing wave with a small boat sailing atop it. And then, with one final casting, he extinguishes it.

"Bueno." He stands. "Shall we gather the cowboy and discuss our next steps, then?" He surveys the group once more. "Oh, and does anybody need more healings?"

As he hurtles towards the keep, Nirzeg realizes that he will need to spend some time researching some way to control these skeletal horses. But from what he knows about summoning and raising dead, it seemed that the magicks binding these horses are somehow different from your average, low-powered necromancy. 

"Time I do not possess it seems." He finishes aloud, blissfully unaware having attempted to give chase while Wickerman stayed behind eyeballing Ab-sama's fire spirit. "Well old chap. Thanks for the lift at least, I suppose." Nirzeg said as lightning began crackling off a drawn longsword. "This... This is gonna hurt me more than hurts you." With that, after affirming his grip with one hand, the other tries to drive the blade straight into the back of the horses neck.

Bonus Action: Nirzeg activates (1st level)[Tooltip Not Found].

Action: Nirzeg Attacks with Great Heaven Cleaver Attack: 22 Damage: 7.
Plus an additional 5 thunder damage if it moves.

With a groan and many cracks, the horse is shot through with magical energy and breaks apart from under Nirzeg. 

The words are quiet, save for the nightlife.

"That was beautiful, Ah'brasar. Thank you." She looks at Derrikoth for a moment. "You still need healing?"

Derrikoth flexes his one uninjured arm, the only part of him that's not covered in dried blood, "I should be able to hold. Thank you, Ah'brasar, for your helpful intervention. These fiends that we just slayed were the ones that killed Alus. I am glad that they were kept from escaping."

"Took care of the last one, the stubborn bastard. Seemed surprisingly intent on getting back to the Manor of all places. Could be there might be more to these 'Hunt Lords' than a couple of pasty flesh ****ers riding their ******** of a dead ride." Nirzeg said as he entered back on the scene(eventually), having patted his side where experimental bag of holding rested at a hip. "See our resident Phoenix decided to stick around, which says... a number of things." He looks down to the grave for the first time, and a mix of emotion play across his face. Chief among them was a bitterness that soon gets wiped away as the Githyanki looks up to the others.

"Something to figure out fer certain on the way or later. Right now, I say we be thorough. It'd be one thing if the shit lords were the only issue. I rather not come find'n out the place itself spawns 'nd have to ride on back to deal with the issue again." He promptly holds up a finger if he sees Astra or Gene look ready to protest. "Just say'n. If it is, 'nd it's spawning the same spirits to boot. Rather not have'm dog'n us more than a night, thank you  very ****'n much. After we can let birdy here burn the shithole down for all I care -- BUT not before.  Found a secret passage  lead'n down that might just wind up buried if we don't play the cautious game. That, and... the possible coin or other useful acquisitions from previous victims to find." He admits, trying and failing to hide at least a hint of sheepishness at his voice over far too much interest in coin.

(@Away: Put the horse skull into the bag of holding to study and maybe used later for something. If I could only get shards however or some other broken piece, than that's fine too.)

The skull is still intact, and even still has scraps of the worn leather barding attached to it. 

The way to the Keep of the Hunt Lords is open to you, seeing as the front door was left wide open. 

"Please, friends, such formalities are not necessary. You can simple call be Rasa. And I agree with the cowboy. The people of Noaner's Hold will sleep easier knowing we have freed them from the clutches of this ugly curse."

He beckons Sparky over to him.

"My friend here is quite useful but is, ah, how you say, perishable. Unless we take some time to rest for a bit, I will only have another hour or so of his assistance. So I suggest we either move quickly, or we take una poca siesta to recharge a bit, yes?"

Derrikoth sets up shop a bit outside the Hunt Lord's keep, "A short breather would be in order to more efficiently kill any more of the bastards."

Hit Dice: 9 9 13

// You can all take a short rest. Go ahead and roll your hit dice if you're healing, and if you're doing anything else during the hour post here! //

"The **** is a cowboy?" Nirzeg muttered while glancing off to the side and genuinely looking confused for a moment. But seeing at least Derrikoth lean in the direction of a short rest, the Githyanki sighs and rolls his eyes. "O' fine. Whatever. Zeek." After some mental exchange between the two, Zeek lets out an annoyed sounding yeowl before taking back off into the manor to keep an eye on the secret door from some shadowy corner. And if he should find anything hanky going on with it on the room in general, it would report it. Nirzeg, for his part, stays at the very edge of their connection. If that meant being inside or just outside a wall of the manor, then so be it. Either was fine, and it was the closest he would come to compromising if any question it.

Though before taking his own rest in some corner, tweaking and adjusting his gear with a myraid of tools, the first two minutes at least are spent mending Wickerman's injuries prior to sending him off to play guard dog with his catty brother. Soon as the rest was over however, he hardly waited for the others before making a practically beeline for the chest before the secret door, testing out the keys on the dwarf's iron ring.

Notes:
Using Arcane Recovery to get back a 2nd level spellslot following the short rest(if completed).
Using 2 castings of (cantrip)Mending to restore 8 HP to Wickerman, as per Alchemical Servant rules.
Hit Die Spent(Artificer-1): 9.

There are few enough keys that it’s a simple matter of elimination. After trying 3 keys, Nirzeg is able to open the antique chest. Like the rest of the keep, the chest is covered in dust. But it’s what is inside that catches the eye:

The chest contains 600 gp in a gray sack made of what appears to be stitched orc skin, a leather pouch that holds six gems, and three items with magical properties, each wrapped in squares of silk.

The first is a a flexible vest made from a shiny metal. 

The second is a transparent potion in a glass bottle. The potion has a single, curved sliver of some kind of material floating around inside it. 

The third is a tiny pouch with a small amount of glittering dust inside it.