- Recipe: Transmute Water to Undeath
- Requires Alchemy (275)
- Use: Teaches you how to transmute Essence of Water into Essence of Undeath
- [Essence of Undeath]
- Requires Essence of Water (1)
- 1 Charges
Transmute: Water to Undeath is a sub-skill of Alchemy which allows the Alchemist to change 
[Essence of Water] into 
[Essence of Undeath]. In order to perform the transformation, the alchemist must have a 
[Philosopher's Stone] and a skill level of 275.
Transmuting essences will trigger a 24-hour transmute cooldown.
Source
The recipe is a rare, random drop from various high-level mobs throughout the lands, although its use is subject to question, since [Essence of Undeath] is considerably more common (and hence less valuable) than [Essence of Water].