In addition to the important choices that directly affect the game's endings, The Blood of Dawnwalker features several other decisions with consequences significant enough that they're worth covering separately. One of them is whether to kill or spare Xanthe during The Cycle of Love.
Deciding whether to kill or spare Xanthe is a choice you'll have to make if you reach the end of her questline. After defeating the boyaress in combat, she'll tell you her story and you'll have to choose your responses to determine her fate:
As for the actual consequences, sparing Xanthe turns her into an ally during the final stretch of the game. She recalls her Blood Guards and removes some of the supernatural enemies standing in your way during the final assault, while also allowing you to avoid a trap sequence. This makes part of the endgame considerably easier.
However, killing Xanthe has a major advantage of its own: you can drain her blood after defeating her and unlock Blood Surge, a powerful Vampirism ability. Killing her also puts an end to the gruesome measures she has been taking to keep Chariklea alive.
So, which choice is better? From a purely practical perspective, both have strong advantages: spare Xanthe if you want an easier final assault, or kill and drain her if you want Blood Surge immediately. The moral implications of the decision are considerably murkier.
If you spare Xanthe, or simply want another way to obtain her blood, you can find a Phial of Xanthe's Blood in Svartrau City. This means that you don't have to kill her to unlock Blood Surge.
Head to the Cathedral Complex in Svartrau City. At night, reach the side of the cathedral with the large rose window and the cross visible above the roof.
To the left of the cross, you'll find a tower you can use to enter the cathedral, following a route you may already know from the search for the Sword of St. Mihai. Once inside, make your way down to the lower level from the scaffolding.
Defeat any enemies in your way and look for the Belltower storage area. Inside, inspect the ledger on the table: rotate it to reveal the Treasury Key attached to it.
Use this key to open the Cathedral Treasury, located in the northeastern garden of the Cathedral Complex.
There's plenty of loot inside. Head upstairs and look for a small golden chest similar to the blood reliquaries you may have encountered during Xanthe's Recruiters. Inside you'll find a Phial of Xanthe's Blood.
Consume it from your inventory to unlock the Blood Surge ability in the Vampirism skill tree.
