A robe of gentle repose was a garment that when worn would halt the decomposition process. This was especially valued by undead who wished to maintain the appearance of still being a living creature.
Especially prized by undead who wished to masquerade as living creatures or simply did not want their bodies to decay, the robe could halt all decay and decomposition of a creature's corporeal form whilst worn, operating in much the same fashion as a permanent gentle repose spell.
Around 1372 DR, an example of this item had come into the hands of the lich Umaerh. Thanks to the robe he could still pass for a healthy male drow while he resided in Irae T'sarran's Undying Temple.