Chainblade, Elven (3.5e Equipment)
From D&D Wiki
In its standard sword form, an elven chainblade resembles a thin-bladed longsword of superior craftsmanship. In fact, to the untrained eye that's usually what an elven chainblade is confused with.
In its whip state, however, an elven chainblade is easy to identify as the blade breaks into several pieces, each connected by a long, sinuous strand of braided mithral. In this state, the weapon has reach, so you can strike opponents 10 feet away with it. If you possess the Exotic Weapon Proficiency (Elven Chainblade) feat, you can switch between both states as a free action, effectively allowing you to attack both ranged and adjacent foes simultaneously. Otherwise it requires a move action to successfully switch between the two states.
In its whip state, you can make trip attacks with an elven chainblade. If you are tripped during your own trip attempt, you can drop the weapon to avoid being tripped.
All elven chainblades are made of mithral; other materials simply don't have the combined weight and strength to allow for its unique properties. Like all mithral weapons, all elven chainblades are masterwork weapons.