Like in any other ARPG, there is no need to complete every single side quest inLast Epoch. Unless it is your first playthrough, the quickest way to do the campaign is to skip the quests that do not offer a Passive Point or Idol Slots.
The Corrupted Lake is an important side quest that appears during the fourth chapter in the Imperial Era. It is a relatively simple quest that requires you to go to another timeline to stop a dark ritual being done to raise the Idol of Ruin. Once completed, you will get a few Idol Slots and a Passive Point.
How To Complete The Corrupted Lake
You will first come across The Corrupted Lake questduring The Outcasts and the Empire—the fourth chapter in the campaign. If you have alreadydone the campaign, you need to head over to The Risen Lake in the Imperial Era. To reach this area, travel to The Outcast Camp, and follow these waypoints:
Walryn Outskirts > Imperial Welryn > The Soul Warden’s Road > The Risen Lake
While exploring The Risen Lake, you willfind a Time Rift next to the waypoint. Once you enter the Time Rift, you will beteleported to The Ruined Era, in an alternate version of The Risen Lake named The Corrupted Lake.
How To Defeat The Idol of Ruin
It is a fairly simple layout. Continue to explore the area until youcome across the Prophet of Ruin. You should have absolutely no trouble defeating him, especially if you are fightingafter completing the campaign. If you cannot find him, try lookingon the southeast side of the map, and you will find himnear the waypoint.
Once you have defeated the Prophet of Ruin, you willinvoke the Idol of Ruin. It is a massive mini-boss that deals Void damage. Make sure to have capped Void resistance if you are playing Hardcore before tackling it.
Even if you are Softcore, it should not pose much of a threat. It isa Level 26 mini-boss with a few telegraphed attacksthat are very simple to dodge. As long as you are appropriately leveled with a somewhat decent single-target damage, you should absolutely annihilate it.
After successfully defeating the Idol of Ruin, you will geta Passive Point, threeadditional Idol Slots, and 550 XP.
