Blood of the Willing Puzzle

The party encounters a massive stone door, approximately 30 feet tall, and is made of 4 feet of solid granite. This door is located at the end of The Glimmersea in the depths of The Void Keep, and would be the last puzzle/obstacle that leads to Marwin's Door . The door’s origins are unclear, but it is ancient, and older than Marwin’s Door itself. The door itself is magical, and spells have no effect on the door. The center of the door has a spiral carved into the stone with one of the trails of the spiral leading down the door, towards the party. As they follow the carved design from the door, they see it leads to a large triangle carved into the floor with a circle at each of the 3 points of the triangle. Inside the triangle is an incantation carved into the center, written in the Deep Speech.
The incantation reads: “By three they come; Thy shadows bind. By three they come; and let the creator be judged. By three they come; the blood of the willing shows thy path, come and see, come and see”
To succeed the puzzle, and open the door, 3 party members must willingly cut their hands, and put the bloody hands in the center of the circles at each point on the triangle on the floor. One of the party members must have some physical tie to this door, or to the Far Realm (e.g. Kimlen’s bloodline, or potentially one of the Warlocks that helped Marwin, etc.). Once one person bleeds into the circle, they notice that their blood starts traveling through the carving on the floor, as if it’s being pulled. Once all 3 party members do this, the blood travels up the door, fills the spiral, and opens the door.
Notes:
Context: Kimlen’s blood being willingly given is the key to open this door, which is why Hastur is secretly leading him there, and not trying to actively hunt down, and kill Kimlen (although, Hastur would be actively trying to kill the other party members to isolate, and manipulate Kimlen).
Symbology of the carvings: The spiral on the door represents The Far Realm /Space (like the spiral of a galaxy). The triangle on the floor represents the gateway, and sacred geometry in general- the triangle is the simplest geometrical shape in the 2nd dimension, outside of just a straight line, and thus the most ancient geometric shape.
Backstory on the door: The veil between worlds is thin this far down in the Underdark, and deep into the planet, which is why Marwin ventured this far down to open the door to the Far Realm. Long before Marwin was even born, this deep area of the Underdark was considered incredibly dangerous. Due to this “thin area” some creatures/entities were able to break through the barrier, into our reality, which is where the Aboleths in the Glimmersea are theorized to have originated. The spiral carving is significantly older than the triangle carving, which suggests that whoever carved the triangle did so as a warning about Marwin’s Door.