Chrono Trigger/Walkthrough/Chapter 21

Chapter 21: What Lies Beyond? (12,000 B.C. second time)

The Magic Kingdom Revisited

This is your last chance to revisit the magic kingdom of Zeal before it crashes into the earth. Before you move on, make sure you've already:

Get the two tabs in Kajar, one in the corner of the room facing the bookshelf, and one by scratching the Nu after learning his scratch point in Zeal palace
Visit the two secret rooms in Enhasa and Kajar by opening the books in the order: Water-Wind-Fire. One will give you a black rock, and one will let you fight six Nus for some Tabs.
Talk to the girl who was ordered to destroy the sapling in Enhasa and tell her to secretly plant it, Fiona will have the sapling in 600 A.D. and it will activate the sunken desert sidequest.

On your way back to Zeal Palace, stop by the city of Kajar and talk to the Nu running the shop. He'll ask you if the pendant you have is really Schala's, if you say yes he'll say he hates liars, if you say no, he'll sell you the best weapons and armor currently available.

Head into Zeal Palace, where the Mammon Machine will have been taken away to the Ocean Palace underground. You'll get into a fight with Dalton, who's embarrassingly easy. Your only danger is being lulled into a false sense of complacency. The only attack he'll use on you is the Iron Orb, which lowers your HP by 1/2. He'll use it periodically and counter with it when you attack him. Since it only lowers your HP by 1/2 you should be fine, but once you actually work through his 3000 HP or so, he'll finish off with the same technique the Golems used and do a "burp" attack which may deal around 125 damage to each party member. Have someone like Robo or Frog heal regularly to keep the party above a low health level, and you should be fine. Dalton will disappear to the Ocean Palace, and what looks like a time gate will replace him. It'll turn out to be an elevator taking you underground, so it's time to move on.

Challenging Lavos

If you go back and challenge Lavos at this point, you should get The Prophet Ending. There will be a few scenes involving "the Prophet" from this period and particularly nice speech from him, hinting that he would have gotten the chance to do what he wanted without your interference.

Continue to Chapter 22: Lavos Beckons (12,000 B.C. second time)