Quest rules use the June 2016 guide and December 29 patch. The entry location follows the explicit relocation announcement, because the archived quest page still lists the older position.
Before starting
110+. Solar Saint, Twin City (425,246); choose difficulty.
Weekly schedule and boss rewards
From December 29: once weekly on Monday, Wednesday or Friday; unfinished runs resume that week. Pluto awards 3 keys, 3 Yin Jades and 3 Class6 House Packs. Three Treasure Boxes; rankings remain daily.
Walkthrough
Follow these steps in order. Item and NPC names are kept as they appear in the game.
Enter
Give Solar Saint (253,57) 5 Soul Stones from Hell Gate monsters.
Advance
Hell Hall: earn Slayer Points — Archer 600, Taoist 300, others 400.
Clear the crystals
Disable Wraiths guarding 9 Hell Crystals in order. Mirror of Hell lists stage requirements.
Summon the boss
Combine 4 Pluto Token Scraps from Syrens; summon and defeat Ultimate Pluto.
Open the treasury
Follow Solar Saint into Hell Treasury; unlock its boxes with Pluto’s Keys.
Claim rewards
Solar Saint exchanges Dark Horn for 300 minutes’ EXP, Star Sword for Phoenix, Elegant or Celestial Dress. Top 10 fastest claim rewards next day.
What remains unspecified
The archived page does not spell out the crystal order. Exact increased floor EXP and the post-patch box contents are not documented by these sources.