From ThresholdRPG Wiki

Transmogrification is the effect and process of applying a new visual appearance to equipment. Transmogrification may only be performed at Negelem at the Museum of Natural History. The ooc command may be used to determine if equipment may be transmogrified.

The command for transmogrification is transmogrify and several options exist globally, while some, like buying and applying a transmog, may only be performed with Negelem.

The currency for transmogrification is experience points. These experience points are placed in a special pool called reserve via the transmogrify command. Buying, applying, and reverting a transmog deduct experience points from this pool.

Once applied, a transmog must be reverted if you wish to apply another transmog to your equipment. If you lose a piece of equipment from a full set after the entire set has been transmogrified, the remaining pieces will still transmog when the set is activated by equipping, however, you will need to apply the transmog again for all the pieces to match.

If an item is lost, stolen, or requires replacing either by administration or any other mechanism, be advised that such replacements will not come with compensation for reverting/re-application of transmogrification.