There is only one Master Sword. It was made to keep evil out of the Sacred Realm, but after Ganondorf tricks Link into removing the sword in OOT, he gets in anyhow. The Master Sword was then used to keep him in there in OOT. It was indeed made and powered by the sages, which is why in both WW and LTTP, Ganon targets the sages as his way of escaping.