"Oh, I like the look of this place. A little too pointy, though." He carefully avoids a jutting obsidian edge, then turns his attentions to the hellhounds. "Two? Well, that's not so terrible. The left, or the right?"
Once he's given confirmation on their first target, he locks his eyes on the marked hellhound and smiles; he isn't sure the thing understands his intent, but it soon will. "How lucky for you, going first!" Making two swift slashes through the air, darkness arcs from the end of his blade, flying towards the hound. The first goes wide, but the second finds its mark, and cuts into its flesh.
"Whatcha talking about Ash? The pointy bits are the best part!" Nib backs up a bit to get a running start and sprints for the nearest cluster of Stalagmites. "You lot keep him busy on the ground. I'm gonna see if I can get a better vantage point, yeah?" Nib activates his Slippers of Spider Climbing and hops from one Stalagmite to the next, gaining speed and height with every jump before vaulting off the point of one and latching on to a nearby Stalactite. Using the cover of the Stalactites Nib scampers along the ceiling like a lizard until he finally crawls onto one looming precariously above the Hellhound Ash attacked. Nib latches on to the stalactite with his feet and hammers away at the obsidian with his fists, hoping to shake it lose and send it crashing down on the unsuspecting beast.
Spending 1 Ki to use Step of the Wind to Dash and double jump distance.
Athletics Roll to vault off Stalagmite and latch onto a Stalactite: 1d20+8=16
Acrobatics Roll to not take damage from pointy bits: 1d20+11=19 Pass!
Making 2 Unarmed Attacks and using Martial Arts to make a 3rd with my Bonus Action.
Attack Roll: 1d20+7=26, 13, 21
Damage Rolls: 1d6+7=11, 11, 9
"Ah," said Xandra. "Hellhounds. Well. I suppose there's only one thing to do, then..."
And she gave a baleful glare to that one, the one on the left, and moved around to face it, taking the chance that the pair would flank her-- better her than her allies, after all. The spirit of vengeance glowed in her eyes; her sword blazed with holy light! Her battle-cry was a shriek of rage, but it was planned rage; her blows would surely set up Alessia to finish the creature off, and--
OOC: Movement: Right up to the one on the left there, in front of it so someone can move up on the side of it and not be between the two of them. Bonus Action: Channel Divinity: Vow of Enmity! Action: ATTACK! I will make the attack rolls first; what I roll will affect things. 20, 24 so both hit. I will use both second level slots I have to Divine Smite twice! This does an extra d8 per hit, because hey, FIENDS! And... 32 and 19 damage, 51 total, so, uh... yeah. Worth the slots for one of the pair to never, ever get to use Pack Tactics.
-- or, of course, the creature could vanish into a cloud of fur, blood and smokey flame, letting off a despairing howl as it was dispatched back to the abyss. Xandra felt a surge of triumph tempered by a bit of guilt. She didn't intend to hog all the enemies, but sometimes, a Paladin just had to Smite a... fiend. Yes. That was the word. Fiend.
Alessia steps in after Xandra, but as the paladin cleaves right through her target, she switches her attnetion to the other hellhound, the one the mirror images of Tik are swirling confusingly near, and lashes out at it, but unfortunately the tip bounces off a stalagmite on the way.
It's driven back a step by Ash's eldritch blast, right into the path of an obsidian stalactite that falls from above, nearly skewering it! It howls and whines, it's fierce bluster gone in a moment. It turns its burning gaze on its most hated foe, a paladin.
The hellhound bounds over to Xandra, shrugging off the pain as Tik bashes it with his enchanted staff, and vomits forth a gout of smoke and hellish flame. The fire washes over Xandra, but her reflexes and Goddess-given blessings protected her from the worst of it!
But it was an empty act of defiance. Against adventurers such as these, a weak monster like a hellhound didn't stand a chance!
Regarding Nib's action, a rule of thumb I try to run games is that players taking the effort to be cool aren't penalized for doing so. Which means that your 'drop the obsidian stalactite on the hellhound' maneuver has to be at least as effective as if you had just punched it. Since two of your strikes on the stalactite would have hit the hellhound, had you attacked it, I'll say the stalactite does damage equal to those two hits, +3 for the stalactite, for 23 damage.
The hellhound moves, triggering an opportunity attack from Tik. Opportunity Attack!: 1d20+7/1d8+422 (screw up the roll formatting, hits for 8 damage.
The remaining hellhound breathes fire at Xandra (hitting only her).
It's Varuuc's turn, then everyone else, then the hellhound if by some miracle it lives!
The jagged obsidian stalactites and stalagmites give everyone Half Cover (+2AC and +2 on Dex saves) against any attack from further than 5' from the target (i.e. if not adjacent).
If you use the dash action you need to make a DC10 Dex save (no bonus for cover), or take 3 Slashing damage due to cutting yourself on the 'teeth' of the cave. Alternately, you can make a DC 10 Dexterity(Acrobatics) check to avoid the damage.
If a target is pushed back fro any reason, it takes 3 Slashing damage in addition to any other effects.
The Hellhounds are Medium. Their AC is 15 and they have 45 HP. They are immune to Fire. Their saves are ST+3 DX+1 CN+2 IN-2 WS+1 CH-2.
Varuuc steps forward, axe aglow. He slides the edge of the blade over the armored vambrace on his forearm, letting the steel make a sharp scraping noise. Firefang's glow flickers, the light swirling across the blade in imitation of a real fire.
"Over here, dog! That's it, pay attention to the axe. Looks familiar, doesn't it? Yeah, it must look just like home for you. So, let's send you back home, shall we?" The last is addressed to the rest of the team as Varuuc's gaze plays over them briefly before he strides forward.
His first swing of the axe misses, going clean over the hellhound's head, but he catches it on the backswing. He buries Firefang into the beast's side, growling a challenge as he does so.
"I'll see you returned to the hell you crawled out of, dog!"
After wrenching his axe free, he stares down the beast, locking eyes with it.
First attack: attack 9, so that's a miss. Second attack: 24, with 13 damage. Not too shabby. Okay, rolling Performance to keep the hellhound's attention on Varuuc: 21, so here's hoping that's a success. If I can keep the hellhound attacking Varuuc, he'll cast Shield as his reaction if that would cause the hellhound to miss him.
All four Tiks shake their heads and swing on the Hellhound's rump. One of his Mirror Image's staves swept harmlessly through the beastie, but his actual shillelagh did not connect as it struggled with the others.