The Corrupted Seren Stone is the largest piece of Seren which is located in the Hefin cathedral in the Hefin clan district in the north-west part of Prifddinas. Inside the cathedral reside Hefin monks. These monks sell cleansing crystals for 110,000 coins each which can be used on the Corrupted Seren Stone for 9,800 Prayer experience each, if uninterrupted, over two minutes. When the Voice of Seren is active in the Hefin Clan district, cleansing crystals will give an additional 20% Prayer experience, for a total of 11,760 experience.
Cleansing one crystal completes the hard Tirannwn achievement A Clean Slate.
|Coins per XP
||With 1 First Age item
||With 2 First Age items
||With 3 First Age items
||With 4 First Age items
||With 5 First Age items
|With Voice of Seren
||With Voice of Seren +1 First Age item
||With Voice of Seren +2 First Age items
||With Voice of Seren +3 First Age items
||With Voice of Seren +4 First Age items
||With Voice of Seren +5 First Age items