I trapped Mercer Frey's soul

...and I need some suggestions for how to use it. Currently it is in an alchemy satchel for safe keeping while I finish Thieve's Guild. The highlight of this playthrough is when I "trapped" him with DeathLords in Snow Veil Sanctum while I finished and waited by the door. I carefully looted every single corpse while listening to the Disarm Symphony with a smile on my face. So I'm looking for a creative combination of useless item/useless enchantment to name Mercer Frey and carry with me everywhere...