Maybe it requires you to have defeated old king at least once on the save file and further loops only need Mabel.
From your post, it sounds like you haven't touched the chaos dungeon yet. Did you go there and talk to Mabel when she appears at the bonfire before checking the dlc 3 door?
Do ashes reignited, left of the chaos dungeon bonfire. Requires you to beat a boss in the dungeon first though I think. At the end of it you can get 50 old one souls (get the mystery as well at some point, it's a great head armor) which are +300 all stats and the run itself gives you about 18m souls if you have 2x soul. You can spend those on more old one souls in the chaos dungeon.Alright, thanks
Btw, is there a more efficient way to raise your stats in this game? Collecting a lot of souls and then spending it on colored souls (Limited to 99) just for a minuscule stat boost is pretty repetitive. Is there no other method to increase base stats faster?
From your post, it sounds like you haven't touched the chaos dungeon yet. Did you go there and talk to Mabel when she appears at the bonfire before checking the dlc 3 door?