Mourning's End Part II/Quick guide

Starting out

 * Talk to Arianwyn in Lletya.
 * Wearing your mourner gear, talk to the head mourner under the hideout in West Ardougne.
 * Run west through the cave, keep going until you find the dead bodies.
 * Search a guard corpse for a colour wheel.
 * Report back to Arianwyn in Lletya.

Temple of light

 * Go back to the temple and climb the staircase to the west of the entrance.
 * Run south and climb up again.
 * Run to the centre of the eastern wall. Chip off the black crystal.
 * Return to Arianwyn.
 * Use the crystal on Eluned (right next to Arianwyn). Speak to her again for a new crystal.
 * Talk to Arianwyn again.

Blue door

 * Return to the temple with a weapon and healing familiar if possible.
 * Ascend the stairs.
 * Pull the crystal collector on the eastern wall.
 * Collect all 5 items from the collector.
 * Use the handholds on the south wall and enter the door and loot the chest.

Magenta door

 * Pull and collect from the collector.
 * Pass the door and loot the chest.

Cyan door

 * Pull and collect from the collector.
 * Climb down, through the door and loot the chest.

Yellow door
Note: Do not reset the system or you will have to repeat the previous steps.

Magenta and yellow doors

 * Pull the lever and collect everything at the collector.
 * Loot the chest.

Cyan and black doors

 * Pull the lever and collect everything at the collector.

Finishing up
If you do not have a death talisman/tiara/hood, read the full quest guide for what to do next. Do not lock yourself out by teleporting.
 * Pass through the white door.
 * Enter the death ruins.
 * Use the newly made crystal on the altar.
 * Use the crystal on the black crystal (top floor).
 * Talk to Arianwyn.
 * Quest complete!