Drawing Demons: Biblically Accurate A̴͙̿n̶̙̕g̴̻̾e̸̛l but Something's Ẅ̷̼́r̵̻̉o̵̘͂n̶̥̊g̷̙̽... Part 1

Another Eldritch Horror creation for my Dungeons & Dragons 5e campaign, Aeon of Silence.
It's name in Greek (As it's what I use for the Gnome language) is the Ftera tou Theou, which loosely translated to "Wings of God", and if you want to use it in your campaign, a statblock will be provided at the end of the description.
Audio Used (In order of appearence, with links)
Black Waters - Myuu • Black Waters - Myuu
Angst - Myuu • Angst - Myuu
Sea of Black Tears - Brütal Legend OST • Sea of Black Tears
Chamber Below - Skullgirls OST • Chamber Below
Parasite Eve - Bring Me The Horizon (Outro) • Parasite Eve
Fterá tou Theoú (Fterr-ah-tuu-fey-oh) "Wings of God"
"A flying creature with four heads, at least one being a man's and the rest being of beasts. It produces evil life-draining radiance as it drips Black Oil. Its multiple heads scream in eldritch tongues, acting as watchdogs and commanders for lesser Fántasmata."
CR:17 (Prof:6) / Large Celestial Aberration (Neutral Evil)
AC:20 (Divine Grace) / HP: 150 (20d10+40) / Speed: Fly (Hover) 40ft
STR: 8 / DEX: 18 / CON: 14 / INT: 13 / WIS: 23 / CHA: 13
Skills: Acrobatics(+10) / Deception(+7) / Investigation(+7) / Perception(+12)
Damage Immunities: Necrotic, Poison, Radiant
Condition Immunities: Charmed, Exhausted, Poisoned
Senses: Lifesense 65ft, Devil's Sight 120ft, Passive Perception 22
Traits
Call of the Hive: Black Tear creatures with an Intelligence Score greater than 6 are linked in a Hivemind.
Each Black Tear creature shares a telepathic link to others within a number of feet equal to their Wisdom score multiplied by 100.
If large groups or especially powerful individuals are slain, nearby Black Tear creatures are compelled to investigate, homing in on the slain creatures' last known location.
Lifesense: The Fidia has a Blindsense that only picks up on non-Undead, non-Construct creatures within a number of feet equal to triple its Wisdom Score, rounded down to a multiple of 5.
Watery Grave: When the Ftera takes damage, it releases a burst of Black Tears. Creatures within a 5ft radius of it are subject to the Black Tear Corruption effect. When the Ftera drops to 0 hitpoints, it releases this burst in a 10ft radius and its body disintegrates into the waters of the Black Sea, potentially infecting surrounding natural terrain over the course of days.
Divine Grace: The Ftera adds its Wisdom Modifer to its AC and the Radiant damage of spells. If it slays a creature with Radiant damage, it gains Temporary Hitpoints equal to the total damage its attack dealt.
Innate Spellcasting: The Ftera can innately cast the Sacred Flame cantrip, Guiding Bolt at 1st level, and Sickening Radiance at 4th level. It is always under the effect of a Crown of Stars (At 7th level), and it can make ranged attacks with the Crown's stars under the normal rules of the spell. The Ftera's Crown of Stars effect renews after a long rest.
Legendary Resistance (1/Long Rest): If the Ftera fails a saving throw, it can choose to succeed instead.
Abilities
Multicast: The Ftera uses one of its spells as an action, and spends one use of Crown of Stars as a bonus action.
Guiding Bolt: +12 Ranged Spell Attack, 120ft range, Single target, 4d6+6 Radiant damage, a successful hit causes the next attack roll against the target, made before the end of the Ftera's turn, to gain advantage.
Sacred Flame: 60ft range, DC20 Dexterity Save, 4d8+6 Radiant damage, target recieves no benefit from taking cover.
Sickening Radiance (1/Short Rest): 120ft range, 30ft Sphere, Concentrate 10 min, DC20 Con Save or 4d10+6 Radiant damage, 1 level exhaustion, invisibility blocked.
Crown of Stars (Bonus Action, 7/Long Rest): +12 Ranged Spell Attack, 120ft range, Single target, 4d12+6 Radiant damage.
Beacon of Command (Legendary Reaction, 1/encounter): At the beginning of an encounter the Ftera tou Theou deems a major threat, it emits an eldritch glow and howls to call nearby Infected. A d20 is rolled, if the result is a odd-numbered, 1d4+1 Hellangels are summoned to assist the Ftera. If the result is even, twice as many Assimilated are summoned, instead.
Oily Flap (Legendary Reaction): The Ftera shakes its wings to dislodge any Black Tears oozing along its feathers. All creatures within a 15ft radius of the Ftera must make DC16 Constitution Save. On a fail, taking 9d4+10 Poison damage (Half on success), and suffering the following effects for 10 minutes:
Disadvantage on STR & CON-based attack rolls, ability checks and saving throws.
Healing effects only restore half as much HP.
Target's location is known to nearby Infected
Killing blow turns target into an Assimilated
Black Tear Corruption can be suppressed by Greater Restoration.