A piwafwi is the Cloak of Elvenkind of the Underdark. Although Dark Elves (drow) and their unusual equipment first appeared in the 1978 "Against the Giants" series of Advanced Dungeon and Dragons adventure modules, the word "piwafwi" didn't appear until the 1990 release of R.A. Salvatore's Homeland, the first volume of his Dark Elf Trilogy. "Piwafwi" is a word of drow origin, meaning a cloak. More specifically, piwafwis are cloaks fashioned (of spider silk and some other unidentified fiber) to mask the wearer's body heat to infravision. They are also resistant to fire. In game terms, a piwafwi confers a 75% chance to hide in shadows, and a whopping +6 bonus to saving throws vs. fire.

Like the armor and weapons fashioned of drow adamantite alloy, the piwafwi is destroyed by direct sunlight, becoming useless within 2 weeks of such exposure. Drow nobility and their minions often have their piwafwis embroidered with their noble house's device. Salvatore's novels coincided with the release of a wealth of new material for the Underdark of the Forgotten Realms setting, and the novels spurred a tremendous interest in all things dark elven; it wasn't long before a distinction between "lesser" (common) and "greater" piwafwis arose. Lesser piwafwis only provide the concealment bonus, while greater piwafwis add fire resistance. Neither type shows enchantment to Detect Magic spells, unless further enchanted.

Since drow are notoriously jealous and xenophobic, and their equipment presumably difficult to manufacture, they are extremely unlikely to give or sell piwafwis to non-drow.