The crystal anchor was a drop from Crystal dragons. The weapon used to have a special attack that when used restores prayer fully and drains the other players strength attack and defence by 80%. Many players ranted in the forums, that this item is way to powerful. Jagex changed it to an untradeable crystal seed. This crystal had an "transform" option, which will convert the crystal into another crystal weapon which the player was able to choose from. Odd enough this weapon has a magic damage bonus plus a prayer bonus that making it very popular with pkers but it is very difficult to obtain.