Your next quest is to go to the Temple of the Ancients and find Sephiroth. It's located on an island just east of the Blacksmith's House, in a spot called the Woodland Area. Enter the Temple and do some exploring in the huge maze you'll wind up in. Don't worry, it's not quite as awful as it looks. Just take it nice and slow, and get all the treasures. Also, pay attention to the guy who keeps running away from you--follow them and they'll lead you to new areas. The first one will lead you to a shop, Vincent's Silver Rifle, and a spot where you can save and restore your HP/MP. The second will lead you to a new area, with a bunch of falling, rolling pin-like objects. Try to time it so that you will run and duck under the cut out part of the rock. Once you make it, make SURE to grab the Morph materia, save again, and go on to the Clock Puzzle. Actually, the Clock Puzzle isn't much of a puzzle at all, and I think you can figure this one out by yourself (hint: it's easiest to move the hands yourself). You start at X. At XI is nothing, and XII, we'll get to later. I holds a Monster-in-a-Box (remember those? :-), Jemnisimi, who can be instantly killed with Bio magic if you don't care to mess with her. II holds nothing, and III holds another Monster that is also very weak to poison. Be careful of this one, because its' Draining attack can kill you very quickly if you aren't careful. IV hold the Princess Guard, Aeris' ultimate weapon. Although it's hard to say, I believe this weapon powers up when Aeris' protects another party member using the Cover materia. Correct me if I'm wrong. V holds the Ribbon accessory, a very nice one that protects from all status ailments. VI will kick the storyline along, so don't go there yet if you want to get all the treasures (you won't be able to later, so do it now). VII holds a Trumpet Shell for Cait Sith, and VIII holds a Megalixer. IX holds nothing. Finally, if you let the second hand sweep you off, you'll wind up at the bottom, where a mini-boss awaits. The chest contains Cloud's very powerful weapon, the Nail Bat. When you're ready, head through door number VI.
You'll be faced with another puzzle and another blue guy. Hmm, this seems kinda tough. Actually, you can figure it out eventually, but here's the way it goes. The first number is the door he goes in, and the second one is the door he'll come out of.
Row 1: 1 (9) Row 2: 3 (2), 8 (7), 2 (1), 6 (5) Row 3: 7 (6), 4 (3), 5 (4), 9 (8)
So, if he goes into number 3, he'll come out of (3). Get it? Btw, the chest contains a Work Glove for Tifa, another one of those zero-materia slot, power weapons.
When you can go on, do, and eventually you'll come across a Red Dragon boss. Protection from Fire would be handy right now, and I wouldn't advise using fire-based attacks. You'll get a Dragon Armlet and the Bahamut Summon materia for your troubles. Now, go back to the clock and up to XII. There's another boss awaiting you, and this one's quite a bit tougher. Use Bahamut and whatever else you got, although Demon's Gate is pretty magic-resistant. If you have Aeris' Level 4 Limit Break, it would come in very handy right about now. When you've bested him, Cait Sith will volunteer to get the Black Materia from out of the temple, destroying himself in the process. Cloud will have another psychotic episode, and begin attacking Aeris. You'll then see a dream sequence, where Aeris talks to you. Then Sephiroth appears, and follows her. You'll awaken in a bed in Gonanga Village. Go talk to the rest of your party (sans Aeris), and you'll discover that the next place you need to go is the Bone Village. It's the place where you got those Rune Armlets, remember?.