Once you have rescued Yuria The Witch the tower in the Inner Ward by finding the Fat Official’s outfit and making your way through the Inner Ward, unlocking the Tower. She will then go to the Nexus where you can purchase the Spells she has on offer providing you have the correct Demon Souls / souls to purchase the Spells
The Demon Souls required for Yuria are
- Hard Demon Soul ~ Armor Spider
- Dragon Demon Soul ~ Dragon God
- Golden Demon Soul ~ Old Monk
- Pureblood Demon Soul ~ Maiden Astraea
- Silver Demon Soul ~ Penetrator
- Soul of the Old One ~ Maiden In Black (end game) You need to hit the Maiden In Black (unlocks the Seekest Soul Power Trophy as well as the Old Ones’ Soul)
The Spells that Yuria will sell you and the Souls required to unlock them are