Talk:Adept's Hat/@comment-162.201.198.241-20150615061934/@comment-24458380-20150615162231

The only other equipment that also extends the duration of sigils are Bitterblack Armor Lv.3 head armor. Namely, the Grave/Carrion Veil, Hood of Shadow/Oblivion, and the Nether/Hellfire Helm.

But be advised that this bonus enhancement occurs "randomly" during the purification process, with no guarantees that the head armor you get will have this bonus effect.

Refer to the "Bonus enhancement" page if you'd like to see which spells are affected by this effect.