At first I thought my Crossworlds game was bugged.

Every time I would buy units inside of the Wizard's Tower on Debir, they disappear whenever I exit the Wizard's Tower.

Before I made this post, I tried to search for this problem online, and I found one guide that says they are supposed to disappear when you leave the Wizard's Tower, but that guide also says that you can use them while you are inside of the Wizard's Tower.

Except, I can't even do that either.

Because the Shops of a particular floor only become available to me after I defeat the Wizard on that floor.

But then if I buy units from those shops, as soon as I go up to the next floor (where I need to go to fight the Wizard again), then the units that I had just bought on the previous floor of the Wizard's Tower automatically disappear out of my army just before battle too (even though I did not exit the Tower).

So then, it appears that the units for "sale" inside of the Wizard's Tower exist solely to troll the player, and they have no other purpose, besides trolling the player?

Unless either:

a) I'm missing something, or
b) the GOG version of the game is bugged.

Can some veteran of this game please explain this problem to me, and tell me what is actually going on here?

Not being able to take the tower units outside doesn't mean the game is bugged - the tower is a self-contained arena to test your ability to wage combat with randomised troops you didn't choose and what goes on in the tower, stays in the tower.

The challenge is to:

1) Prepare ONE troop of your own which you will be allowed to take into the tower.
2) Outmanoeuvre the guardian / keeper on the first level and "buy" units at the dwellings (for 0 gold each). You should be able to buy them without killing the keeper first.
3) Win against that floor's guardian
4) Repeat on the next level until you reach the top of the tower and get a prize. Yes, the troops from the previous floor will disappear (except the one you choose to keep) and getting to the new floor's dwellings unharmed is part of the challenge.

NOTE: All of your own troops that you entered the tower with will be returned to you when you leave - you needn't worry about stashing them someplace else first (and the troop that took part in first floor's combat will be fully regenerated).

The way I approached it (when playing on Hard) is that I visited it from time to time as my hero gained experience, spells and artefacts - I would usually do this close to gaining a level, so that winning a tower floor fight got me a level that I could then use to progress further in the overall game world. The later encounters are relatively difficult; I beat them well into the game - you aren't supposed to win the tower early.

Thanks for your thorough post, -Iota-.

This is the part that was contributing towards why I wasn't understanding what was going on before I had read your post (and the other reason is because the game itself does a horrible job of [not]explaining any of these things, which the Wizard himself doesn't even try to explain at all even if you ask him how the Tower game works): Now that I tried doing what that quoted text says, I can see what you mean.

If I was going to restate your point in a way how I now understand it thanks to what you've said, I would say:

The shops in the Wizard's Tower are designed to bolster your army with some more units, in addition to the one unit that the Wizard allows you to choose to fight with on any given floor; but you can only "buy" those extras if you are able to reach the shops that sell them before the Wizard bumps into you.

I'm sure this thread will also be useful also to clearing up the confusion of other people who will find it in the future via google searches, and/or via browsing GOG's forums.