This is commonly known, but it's kind of a nice thing to try. When in the End of Time, talk to any of the teammates who aren't currently in your party. When they ask to join, agree, and that character's theme music will fly until you exit.
That's right, Schala can join your team. Throughout the game, you will have a chance to fight her mother. Do so and play the rest of the game. Now, when you can select New Game +, play until you reach that part, then slee instead of fighting. The city will eventually fall, and Schala is on the remains. Find her and she'll ask to join you.
There are a few ways of getting it, but this method is the easiest. When possible, travel back to 65,000,000BC and go north on the map until you find the Hunting Range. There are many enemies, but none oppose a threat, except one. And that's the one we're looking for. When there, go north until you find an odd vine hanging from a tree. Blimb up it and go south until you find a small clearing. Wqait there until it rains and a Nu should pop out of the trees. (A round blue monster) Engage it in battle and be careful. When he hits you, your health will go down to 1 HP instantly. He's not too tough, and the Third Eye is well worth it.