Ask Eldritch about all your new spells, then go back over to the portal and [A]ct to say "Springdale Valley".
When you arrive, head west of the portal until you see mountains. You'll probably meet Brother Stanley along the way. If you need healing around here, Stanley's your guy. To the north you'll see a cabin. That's Oscar's tailor shop. Talk to Oscar inside. Buy a vest and a black bowtie from him.
Brother Stanley
Tailor Shop
Nice Interior
Oscar
Walk over to the mirror and [L]ook at it, then [A]ct to learn Reflection.
Now go to the rack at the north end of the room. [L]ook at the vest on the rack, then [A]ct to try it on. A piece of paper will fall out. [L]ook and then [A]ct on it. Done!
Fun fact: This does not seem to affect the way the rest of the game unfolds, but if you want, you can kill Xavier now, if you hadn't before.
Here's how: Return to Fairhaven Valley, use the third set of diamonds to make more coal, and go through Xavier's dungeon again. Just after you pass the skull, you'll meet Xavier as usual. Run away from him. Then cast Detect Monster, Quickness, and Reflection, all at once.
You'll see Xavier on the map again. This time head straight for him. Cast Energy Blast to take out his companions and it will land first since you're fast. Then, the following will happen, which is very satisfying:
Ha ha ha haaaaa! Anyway, where were we? Springdale Valley...
Wander around on the map, generally to the northeast, until you encounter Billy the Kid. This may take a while and involve much running from combat.
Mountain Lion
Banana Peeler
Giant Lizard
Wabbit Hunter
[T]alk to him and his goat will eat your vest, leaving behind some buttons. Let him join your party, then [G]et the buttons.
Billy The Kid
Your wanderings probably took you to the northeast corner of the map. If not, go there now, and [A]ct to enter the bakery. [T]alk to Elizabeth, and inquire about her ice skates. Buy them from her. Next, [T]alk to Charles and agree to cure his lycanthropy, then ask him about everything else. Buy a cookie from him for the heck of it. (He "looks happier than you've seen him in months," but the last time you saw him was when you brought Veronica back, so... Huh?)
Bakery
Elizabeth
Charles As A Baker
Anyway, exit the bakery.
Take eight steps south and you'll blunder into a rabbit trap.
Go ten steps west, and two steps north, and you'll blunder into another rabbit trap.
Go six steps east to the ruins, and four steps north, and you'll blunder into a third rabbit trap.
Four steps west and one north, and you'll see an animal den. Go inside. [T]alk to Kimberly the Rabbit and she'll present you with a carrot. [G]et it and leave the den.
Kimberly Rabbit
Go southeast, past the ruins. It's hard to see on the map, but there's a cave here, with a sign reading "The Bat Cave". Go inside. The bats here all breathe fire and can insta-kill you, which is nuts. Avoid them and walk around to the northeast corner and you'll find a velvet case. [A]ct to open it, and you'll find a festive flute, which will appear as "silver flute" in your inventory. Leave the cave.
Giant Bat
Go south from the cave until you hit mountains, then go east and meet the troll. If she serves you tea and then forces you to retreat, check and make sure that Billy the Kid isn't paralyzed or dead. See Brother Stanley if so. If Billy is alright, he'll distract the troll and you'll sneak across the bridge to a cave. Go inside.
Theresa
Head south until you get a really blatant clue that there's a secret door. Go through it, and you'll find a metal rod. Instead of just picking it up, you'll need to [A]ct on it, then [G]et it. Walk north and you'll find another secret door leading you out of this room.
Keep wandering down the corridor until you find an ice tablet. [L]ook at it, then [A]ct to learn the Strength spell.
We're not quite done here. Keep going until you notice "a glint of silver in a slab of ice." [L]ook at the slab, then [A]ct to break the slab. You'll find a lovely sword you can equip. Proceed generally east and you'll find another exit. Use it and you'll appear on an icy plain surrounded by snowy mountains.
Snowy Mountains
Snowy Forest
Polar Bear
Ice Worm
Walk around a bit to get your bearings. There's a path to the south, but you'll need to [A]ct and put on your ice skates to traverse it. Once you're through that, head southwest and you'll find an igloo. [A]ct to clear the snow from the entrance (you still have that shovel, right?) and go inside.
Igloo Exterior
Igloo Interior
The only occupant here is the apocryphal "Edward the Eskimo." [T]alk to him and learn about his kayak and his troubles catching fish. End the conversation and [C]ast the Time Distortion spell. With his larder full, Edward will give you permission to use his kayak. Head back outside.
Edward
Go southeast and you'll find a kayak on the shore. [A]ct to board it, and paddle your way south. Soon you'll find a pengiun. [T]alk to him. Then, even though he doesn't show any interest, [D]rop your bowtie on him. He'll take it and give you some key advice. That's all you need from him. Paddle north and return the kayak to the spot you found it.
Igloo Exterior
Penguin
Walk over to the igloo, then take two steps north. [A]ct to build a snowman. The carrot, buttons, and corncob pipe will leave your inventory, and the snowman will join your party.
Snowman
Walk back to the igloo, then head east. Your new friend will win a battle with a yeti. Keep going and you'll find an ice grotto to the south. Walk right in. You'll soon find a man frozen inside a giant hourglass, and your snowman friend will give some weirdly specific advice about what to do. [A]ct to blow the silver flute.
Yeti
Azersun
Around the corner you'll find a tattered piece of paper. [L]ook and [A]ct on it to learn the Depoison spell. Business concluded, leave the ice grotto.
Walk back to the northwest and the cool cave entrance, and go inside. As you begin the journey back to Springdale Valley, your snowman friend will stay behind. Exit the other end of the cave, and run back across the troll bridge on the map. Billy the Kid will rejoin your party.
[T]alk to Azersun, who has joined your party. He'll suggest a trip through time. Go for it!
Now that you're back to the past like Samurai Jack, make your way east. Eventually you'll encounter a huge wolf. Do battle with it and slay it. The corpse will regenerate into a human named Malcolm who immediately joins your party. [T]alk with him and learn a few things.
Malcolm
Hike over to the pyramid - probably northwest of you - which is now intact, and go inside after Malcolm. Once you're in, [C]ast Light and take a single step south. Malcolm will give you some good advice. [C]ast Detect Monster and you'll see a horrible thing on the other side of the wall. That's the Devourer.
Ruins
Ruins Pre-Ruining
Devourer
Take a few more steps south, then [C]ast Time Distortion. Book it through the door to the south, into the room with the Devourer. Head to the east wall, then go north until you make it out of the room. Hopefully the Devourer won't catch you.
Head west and up the ladder. Walk through the next two rooms and the metal rod in your inventory will absorb the electricity. Up the next ladder. Go into the next small room, then south to another small room. You'll be freaked out by your own shadow. Turn off your Light spell, then try walking through the room again. Turn the Light spell back on. Another ladder! Up you go.
This pyramid appears to be a monument to capitlism. On a nearby altar is a pot of gold. [G]et it, and the whole structure will collapse. Yep, that's capitalism! You're outside again.
Head west and you'll come across a wigwam. [L]ook at it, then go inside. The interior looks suspiciously cabin-like. [T]alk to Alphonso, a character who has definitely aged badly in the cultural milieu. Ask him about everything, then leave the wigwam.
Wigwam
Alphonso
Head north and east along the top of the map until you spot a strange tree with a knot in it. [A]ct to knock on the knot. Inside you'll meet Lucy. [T]alk to her about various things, then [D]rop the pot of gold on her. Take the diploma she gives you straight back to Alphonso in the wigwam, and [D]rop it on him. Job done!
Lucy
Exit the wigwam and head to the extreme northwest corner of the map. You'll find a bottle floating in the river. [L]ook and [A]ct on it to reveal a piece of parchment. [L]ook and [A]ct on that to learn Unparalyze.
Forest With Path
Flooded Valley
[T]alk to Azersun to return to the present. Before going, you might want to check out how cool the bridge looks without the troll around, the construction site where the tailor's shop will be, and the dam in the river.
Dam
Future Shop
New Bridge
In the present, walk to the bakery in the northeast corner of the map and go inside again. [T]alk to Charles, making sure to greet him, and he'll thank you for lifting the curse and hand you a map. Make sure you have it, then exit the bakery.
That's all you needed to do in the present for now. [T]alk to Azersun again, and go back to the past. This time, walk to the southwest region of the map, to the Wizard's Enclave, and go in.
[C]ast Light, then Detect Monster, then Time Distortion. With these spells active, go into the next room and weave between all the hunky bouncers to reach the next door. You may have to cast Time Distortion again partway across the room.
Bouncer
Feel free to turn off Detect Monster now. In the next room, Alizarin is instructing some students. [T]alk to him, and greet him. You'll be volunteered as a victim for a few spells, and then allowed to pass to the next room.
Alizarin
Victor is in this room. [T]alk to him, then [C]ast Energy Blast as he requests. What a cool demonstration for the class! Continue to the next room, which is empty, and then to the room beyond that.
Victor
Sinth is here, looking like Janet from The Rocky Horror Picture Show. [T]alk to her and you'll be asked a series of questions. The answers are "nothing,", "fifteen", and "thimble".
Sinth
Proceed through to the final room and you'll encounter two pedestals. [A]ct on them to fill out your spellbook. If you've followed this walkthrough, the only spell you haven't already learned is Strengthen Portal.
Now turn around and slog your way out of the Wizard's Enclave. [T]alk to Azersun again, and return to the present. Walk south and west until you find the portal.
[C]ast Strengthen Portal, then [A]ct to go to Violet Valley. [C]ast Light, then [C]ast Strengthen Portal again, or camp first if you don't have enough spell points. [A]ct to go to Fairhaven Valley. [C]ast Strengthen Portal a final time.
At this point, assuming you still have the wizard hat from the secret room, you should be able to [A]ct and put it on. Instead it just does what it always does: Fly off your head and land on the ground, in protest of your unworthiness. Harrumph.
[T]alking to Eldritch will end the game, presenting you with a rather underwhelming animation that shows you as a white-haired old fogey, opening your own Wizard College. When that finishes, the computer will just hang. I guess they threw everything they had into the middle, and left nothing for the end.