I wanted to play as a Raven Queen Warlock so I made the subclass for myself with the help of the Class Template from Gycicada https://www.nexusmods.com/baldursgate3/mods/946 and the Larian Studios Discord.
There are a few things that I was not able to implement exactly as it is in the tabletop so this is my personal interpretation of the subclass.
This is also my first mod so maybe I will change some things in the future when i have a better understanding of how stuff works.
I have not played a full playthrough with this yet so I dont know if everything works yet.
Also this mod does not make any Story changes yet. I might try my hand at that in the future but for now you can choose either one of the existing subclass tags or you could choose to use no subclass tag at all.
Feedback is appreaciated.

Enhanced Spelllist:
Spell Level 1: False Life, Sanctuary
Spell Level 2: Silence, Spiritual Weapon
Spell Level 3: Feign Death, Speak with Dead
Spell Level4: Ice Storm, Death Ward (since Locate Creature is not in the game I replaced it with Death Ward)
Spell Level 5: Cone of Cold, Dispel Evil and Good (since Commune is not in the game I replaced it with Dispel Evil and Good)

Level 1 Feature:
Sentinel Raven
You gain the service of a spirit sent by the Raven Queen to watch over you. Once per short rest (but out of combat) you are able to Summon a Raven Familiar.  If it is slain by a creature, you gain advantage on all attack rolls against the killer until the end of the day. After Summoning your Raven Sentinel you gain Darkvision and a bonus on Perception rolls equal to your Charisma modifier. If you already have darkvision you will gain superior darkvision. If you have superior darkvision or are lvl 5 or higher you will gain immunity to environmental blindness.

Level 6 Feature:
Soul of the Raven
You gain the ability to transform into a raven spirit as a bonus action. You are only able to Dash, Disengage, Help or Hide during your turn (and make an unarmed strike since I could not figure out how to block that). You can transform back using your action.

Level 10 Feature:
Raven's Shield
The Raven Queen grants you a protective blessing. You gain advantage on death saving throws, immunity to the frightened condition, and resistance to necrotic damage.

Eldritch Invocations:
Chronicle of the Raven Queen
Your connection with the Raven Queen allow you to commune with the recently deceased. You gain the ability to communicate with the dead without any limitations associated with the speak with dead spell. (you may need to cast this multiple times on someone to be able to ask all questions)

Raven Queen's Blessing (available at lvl 5)
Your connection with the Raven Queen allows you to prolong the lives of your allies. After landing a critical hit with your eldritch blast you will be able to heal one ally for 1d8 + your Charisma modifier.

note: this is compatible with WinterBrick's Invocations Expanded mod (this mod needs to be under Invocations Expanded in the load order). As a result of this if you dont use Invocations Expanded you will see the Invocation Tomb of Levistus and Lance of Lethargy. This is a result of these invocations technically existing in the game files. just dont take them if you dont use the mod.

icon by necromanzee