Mana-conduits are used to store, transfer, or produce magic. They are typically found in magic items or in Magitech. One could argue they are exactly like enchanted items of old — a sword enchanted with fire simply stores a flame enchantment and transfers it upon swinging. Uses for mana-conduits have evolved, especially when they are being used in conjunction with Leylines.
Mana-conduits can theoretically be made from any item so long as it is able to hold a magic charge. Some materials are able to perform the function of mana-conduit more effectively. The general rule is that precious gems are best at storing and metals are best at transferring. Mana-conduits that produce magic can come in a variety of forms though tend to have a limited amount of charge before they are depleted. There are no guidelines for conduits that produce magic, but it is commonly believed that the more valuable the material, the more effective it is.
Typically, a mana-conduit is tied to a single magic Source. Systems that use multiple sources either have multiple conduits or have a rarer conduit that can utilize more than one source.