Casthor Essence can substantially change eligible gear, but permanently makes the item untradeable and limits further Essence use.
PC / Global, Season 12 The Farside (Sep 10, 2026–Jan 7, 2027)
WHERE & HOW TO FARM
Where to farm
Seasonal gear crafting interface; Casthor Essence is also named as an Agony Wave reward.
Casthor Essence is a high-impact gear crafting material for Rare grade or higher equipment. It can alter Quality or options, with possible multipliers and option changes; the result can improve or reduce the item's value. Once used, the gear becomes untradeable and cannot accept other Essences, apart from Casthor Revitalization Essence. Uses are limited, and restoration requires that Revitalization Essence. Reserve Casthor for a base you intend to keep and whose potential improvement justifies locking it to your character. Inspect the current item rules before committing because results cannot be undone.
Select Rare grade or higher gear that is worth keeping.
Accept that the item will become untradeable and unavailable for other Essence crafting.
Review the item's remaining Casthor uses and any Revitalization requirements.
Compare the candidate item with your current gear and decide whether it is worth a permanent crafting commitment.
Check the item's grade and the Casthor Essence use count in the crafting interface.
Read the displayed warning about tradeability, other Essence restrictions, and possible option changes.
Apply Casthor Essence only after confirming the intended item and accepting the risk.
Inspect the new Quality and options; compare them with the prior item state and your build needs.
If uses are depleted, use Casthor Revitalization Essence only if the item still merits further crafting and the interface allows it.
Equip or retain the result if useful; replace the base rather than forcing more crafts when it is no longer competitive.
Farming tips
Keep Casthor for an item with a strong base and relevant options; the outcome can also reduce its performance.
Treat the no-reversal warning as a real decision point and avoid experimental use on gear you may trade.
Repeat, collect and use
Repeatable on eligible gear while you have Casthor Essence and remaining item uses. Each use has lasting restrictions; Revitalization is a separate, limited recovery step.
Common mistakes
Using Casthor on gear you may sell or trade: the item becomes untradeable.
Expecting other Essences to remain usable afterward: only Casthor Revitalization Essence is allowed under the stated restriction.
Assuming a positive result is guaranteed: options can change or be removed, so compare the outcome before committing further.
When to stop or switch
Stop crafting once the gear meets your build target, becomes worse than an available replacement, or has no remaining uses worth restoring.
