In Demon’s Souls, Yuria the Witch is a character that can be meet and saved. Here’s a guide that will help you locate her in the game.
You will find Yuria in the world (1-3). You will have to get keys in order to save her, first, you have to complete most of (1-3) world, and then go back to the world (1-2) to get another key, and then by using the official’s cap disguise yourself as a Fat Official to gain access to the area she is in. She will be in the Nexus after you rescue her.
Yuria will teach you advanced black magic by using Demon’s Souls. You can see the list in the Magic/Miracles section.
The fat officials imprisoned Yuria for using her black magic during their siege on Bolitaria Palace.
It is indicated that the officials rounded up the witches and executed them due to the remains of Stockpile Tomas’ Wife and daughter holding spice.
Yuria can also be killed by using Firebomb, if you have lost the Official’s cap, then throw the Firebomb near to the first window upstairs to where she is, without lowering down the staircase. She will walk to the edge after becoming hostile and then from there, you can also attack it by throwing arrows.