Speak to Relomia in Heart of Gielinor campsite (west of the entrance). Pick a side or not. (don't bring a familiar)
Defeat Nomad, he uses melee/mage and doesn't use special attacks.
Maze
Solve the maze. Goal is to reach the exit at the far north-east. The solutions to both mazes are found below.
The yellow lines show the main path to follow, the grey lines lead to puzzle rooms off the main map that must be completed to progress along the map later. Go back to the yellow path once the puzzles are complete.
Note: These maps and your minimap may not line up exactly until the puzzle rooms have been completed due to the nature of the maze's mechanics.
Cryptic
Solution
Misery loves company.
All four casters need sad faces
You and I are beautifully broken. The others resent our superiority
Switch broken masks to north (from south) then add gained sad masks to south
When the sun rises, we are happy
Happy faces on both of the east casters, sad faces on the west casters.
I'm bored of helping you, you can figure this one out on your own
NW: Neutral NE: Happy SE: Sad SW: Broken
I'm not a morning person; nor am I a mourning person
Two sad faces on the NE and SE wall, leave the other two without masks.
Never let anyone see how you truly feel, they will use it against you
All neutral expressions on all four casters
Fight
Fight against wights of increasing difficulty, kill enough of them to increase the progress bar on top.
In the next fight it is recommended to kill Nomad first, then Linza and finally Gregorvic. The spirits that Gregorvic spawns will heal him when they reach him.
The third fight is against Sliske himself:
Beware of his special attack where several shadow pits will appear below your feet. Step away to avoid significant damage.
Attack Sliske until he reaches 10,000 health, he will teleport away.
Destroy the Power Source in the centre of the room.
Attack Sliske until he reaches 10,000 health again.
Enter one of the rifts. Sliske will bring you back into the arena.
Attack Sliske until he reaches 10,000 health again.
Jump on the rock formation in front of Sliske.
Defeat Sliske one final time. You have unlimited lifepoints and adrenaline and all ability cooldowns are halved.