Thatch initiative: 14.

.

"How would I know?! I was just being wary of the sceptres!" Fergus calls out shakenly, getting ready to fight.

(Initiative: 8)

Becoming more real by the moment the apparition was stymied from leaving by Sir Almeric and it eventually tried to force its way past him rather than being trapped in a corner, he struck a strong blow across its ivory-like form cracking it somewhat, almost immediately Cainneachs shaft blossomed in its side, though it seemed little slowed by either blow.

( Thatch is up)

As the creature tries to force its way past Sir Almeric, Thatch finishes his draw and releases his arrow right after Cainneach's shot. 

Attack: 22 Damage: 9 plus 3 sneak attack damage on a hit. 

.

(Ori or maybe Tana or the becoming less spectre-y thing?  Aside from Thatch, some real stellar initiative rolls by the good guys!  ;-)

Thatchs arrow thudded into the horrors head, the now thoroughly annoyed thing lashed out at Almeric its serpent arms snapping at him with bladed fangs.

Attack: 7 Damage: 7 + 3 Poison.

Attack: 16 Damage: 7 + 2 Poison.

( Ori, Cainneach, Famh, Tana, Fergus and Almeric are up)

Tana Initiative: 16

Stag - Famh initiative 14

(What kind of damage did it do? All poison?)

Quote from OisinmacCameron >>

The great elk whirls lightly on its feet with a supple grace not usually found in creatures of its size.  While allowing the retinue's arrows to pass unimpeded (in a show of intelligence that is also most unelklike), it moves to block any attempt by the spectre to attack them.  Its antlers remain lowered at all times and it seems to be gathering itself for a charge.  As soon as the undead horror moves to attack Sir Almeric, its coiled muscles unleash and it surges forward like a battering ram in an attempt to knock their foe back from the knight.

===========================

Charge. If the elk moves at least 20 feet straight toward a target and then hits it with a ram attack on the same turn, the target takes an extra 2d6 (10) damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.

Actions

Ram. Melee Weapon Attack: +6 to hit (16), reach 10 ft., one target. Hit: 2d6 + 4 (11) bludgeoning damage.

Or, if the DM will accept the Famhishly* audacious motion to let her use [ability]Tides of Chaos[/ability] on the attack roll, 26

* or perhaps I should call it inFamhish as a fair warning of my tendency to pun people into submission if I ever, Gatanades forbid, throw a tantrum or a gasket

 (edited for completeness)

Almeric is whipped from side to side by the two snake like arms of the Horror, snapping their fangs at him. The first snake head punctures his maille with its fangs, sinking deep into his flesh. Blood runs down his flank as the second blow flies in. Instinctively, Almeric shifts his weight and raises his shield, parrying the second snake head as it thumps into him. Feeling the rush of adrenaline through his body begins, Almeric recognises the first signs of shock. Centreing himself with a silent prayer and adjusting his feet into a defencing stance,  Almeric ensures the Horror cannot easily pass him. His wound closes almost completely and the shock abates. "FERGUUUUS! Finish what you have started. NOW!"

Action = Lay on Hands (Self) +9HP

Bonus Action = Fey Gifts. Fergus has Advantage to his next Attack

(held action for next turn if Famh's knockdown succeeds:

Hooves. Melee Weapon Attack: +6 to hit (13), reach 5 ft., one prone creature. Hit: 4d8 + 4 (23) bludgeoning damage.)

(Cainneach is waiting for 1) Ori's turn, and 2) to see if the menace is Prone, which will make a longbow attack be at Disadvantage.  Ori, I'd guess it's Piercing Damage for the other portion done by the snake arms, but can wait for DMDM to confirm.)

(Assuming there is enought room for Almeric, an Elk, and Ori to stand in melee range of of snake friend.) Seeing the creatures features materialize more and more, Ori thinks there maybe be enough for him to smash with his club. Seeing the snake like extremities strike at Almeric was enough to tell Ori to swing back.

"I thought this was my dance!"

Attack: 25 Damage: 5 bludgeoning plus 2 piercing damage 

Fergus heeds Sir Almeric's words, after all he had no instruction to protect the summon.
With the knight's encouragement, Fergus blasts the entity with confidence.

(Attack with Advantage: 26 [Crit!]  Damage: 15)

Moon-thing Strength Save- 19

Ori smashes into the fiend chipping off great flakes of bone?, Famh charges into the creature in stag form with prodigious strength but its unnatural frame is like hitting stone and it remains standing though battered, Cainneach draws his bow ready to fire as Sir Almeric bolsters both himself and Fergus and Tana considers her options.  Fergus unleashes a great blast of black crackling power that smashes into the creature.....to the sound of a titanic chuckle only he can hear.

( Thatch with Cainneach and Tana still to act.)

( Piercing damage for the 'teeth')

Cainneach is heartened by both the great successes of his companions and by Fergus' seeming return to his senses.  After it appeared his first arrow did some damage, he draws, nocks and looses another.  Immediately after, he calls Salt to heel, imploring the hound to stay out of this fight for now.  It seems unlikely his teeth would leave much of a mark on the stony spectre.

Longbow - Attack vs. Stony Spectre: 26, damage (piercing): 12 w/Hunter's Mark

Salt - Dodge

The elk stamps angrily at its failure to batter Karvala's fetch off her feet, and its frustrated belling echoes through the chamber like the voices that ring from a mighty cathedral's towers.  It now seems to realize that Cainneach and Thatch will likely shoot again (INT of 7); and it refrains from any further attempts to knock the spectre down so long as she does not try to get past its guard and attack the second rank.  Instead, it begins to position itself as if it meant to use its mighty flanks and rocky forehead in concert with the front rank's attacks to back the moon-thing into a corner where it can more easily be dispatched.  The way it is waving its antlers threateningly, though, it wouldn't have any problem using a regular head butt to do it if that's what it took. (readied actions: Charge as an opportunity attack triggered by the attempt to pass; Ram attack or Shove* action as appropriate otherqwise

*Shoving a Creature

Using the Attack action, you can make a special melee attack to shove a creature, either to knock it prone or push it away from you. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.

The target must be no more than one size larger than you and must be within your reach. Instead of making an attack roll, you make a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). You succeed automatically if the target is incapacitated. If you succeed, you either knock the target prone or push it 5 feet away from you.

Quote from EtyenAndiros >>

Cainneach is heartened by both the great successes of his companions and by Fergus' seeming return to his senses.  After it appeared his first arrow did some damage, he draws, nocks and looses another.  Immediately after, he calls Salt to heel, imploring the hound to stay out of this fight for now.  It seems unlikely his teeth would leave much of a mark on the stony spectre.

Longbow - Attack vs. Stony Spectre: 18, damage (piercing): 14 w/Hunter's Mark

Salt - Dodge

"Bonus Action" - After seeing his arrow strike true, Cainneach looks around with increasing concern for Famh!  ;-)