Should you spare or kill Xanthe?
Short answer: Spare Xanthe to make the castle assault easier; kill her if you want Blood Surge from her blood and do not want her alliance route.
The Cycle of Love choice
The decision occurs after the Howling Keep encounter. Sparing Xanthe means she appears in the castle with advice, removes the Blood Guard fight, and avoids her nightmare sequence. Killing her removes that alliance, leaves the nightmare/trap sequence for the assault, and lets Coen drink her blood for Blood Surge.
If Xanthe dies, Coen must also decide Chariklea's fate. If she lives, the later tableau explains that Xanthe continues killing women to keep Chariklea alive. The choice changes the final assault and epilogue state, not whether The Cycle of Love completes.
| Goal | Recommendation | | --- | --- | | Easiest castle assault | Spare Xanthe | | Blood Surge and no alliance | Kill and drain Xanthe | | Preserve Chariklea's tableau | Spare Xanthe |
Source: PC Gamer Xanthe choice guide and PowerPyx Cycle of Love walkthrough.