Violet, distracted by the pain and almost strobe-like effect of the light, misses with her second magical attack.
Tailine, having a stable position to fire on the creature, misses as part of it reforms to avoid the blow.
Estellen's bolt of lighting strikes true, the lightning arcing harmlessly onto nearby objects. As with before, the creature seemingly has no reaction to the hit making it unable to tell what effect if any it has had.
(Jatrin the creature is 10ft up, and therefore out of reach of melee weapons without the reach property)
Avian eyes flaring green Quilqwen incants ”Teine sìthiche” and green lights swirl around the creature (20 foot cube placed high to get the creature but none of my allies. DC 12 Dex save). His gaze travels down as more green light swirls under the shadow being and a shimmering spectral unicorn coalesces on the ground. (Advantage for me and my allies on perception checks to detect creatures within 30 feet of unicorn).
The creature shifts and squirms as the green lights swirl around it, but is unable to avoid them sticking to its body. (the unicorn gives advantage on ability checks to detect creatures in general, but yeah that includes Perception checks)
17 (Jatrin's advantage from faerie fire)
Initially disorientated by the swirling lights, Jatrin manages to find his mark, the javelin piercing the creature and sticking to the wood behind it.
The creature flies across the room, once again extinguishing the lantern. This time though you hear it fall to floor, the glass breaking as it lands. Thanks to the green lights you can still track the general movements of the creature, however it is very hard to tell the exact location of it as it's form blends into what darkness there is.
From there it flies straight at Quilqwen, swiping at him with what might be a claw made of darkness 18 (9 on hit)
As Quilqwen puts up an arm to defend himself from the blow, he screeches in pain. 5 thin, but deep gouges that go down to the bone are now visible, blood flowing from the wound. His voice becomes slightly muffled and his vision begins to darken as the darkness continues to wash over his senses.
The area is once more dim light causing attacks against the creature to have disadvantage.
Quilqwen you need to make a DC 10 Concentration check (for faerie fire) and a DC 11 Constitution saving throw or be blinded until the start of the creatures next turn.
"Light the fireplace!" Quilqwen's form then shifts as legs sprout from the sides of his body, his feathers melting into a black carapace. As the giant wolf spider forms the unicorn races over to center on the creature once more.
(As I now have blind sight with in 10 feet would that negate the disadvantage from the dim light and let me strike with advantage from Faerie Fire?)
This post has potentially manipulated dice roll results.
Violet, now seeing her target lit up, casts, Chromatic Orb attuned via the crystal in her hand. She pays extra attention with this attack (if it hits) to see if it hurts/heals/or is nullified upon hitting this thing.