Trying to train at Newcastle, but I'm told I've learned all I can. I'm at Level 20. Is that the max level for the Clouds side of Xeen?
Thank you.

Exactly what I was looking for. I wanted to do all I could on Clouds before going to Darkside...I'm a little OCD that way. :-)
One I specifically remember was in Golem Dungeon, after defeating all the Golems...I was granted "Golem Destroyer" status (or something similar) and rewarded with "+1 Level" for all.

On Darkside, you can be trained up to level 200. By using certain potions you can push that to about 240 or so. It's theoretically possible to reach level 255 (physical limitation of the variable, it can only go up to 255) but I don't think there's enough potions in the game to get that high, even if you save them all to the end.
My favourite part of World Of Xeen is that you CAN'T do everything you could do on Clouds before visiting Darkside. MUAHAHAHAHA!
There are keys on Darkside to dungeons on Clouds (and vice versa). :P

I liked that too (I originally played Xeen 15 years or so ago), how the two sides combined to form new quests & such. The only thing I haven't done on Clouds (that could be done stand-alone) is the upper right volcanic area. I'm just taking too much damage from the lava & such. Although I did get the Ever Hot Lava Rock for its quest.
Looking forward to traveling over to the Darkside now!

There are 2 locations in the lava you can visit before entering the dark side. They'll be challenging but doable at level 20 with the right preparation and tactics.
You might want to keep a save from just before entering darkside so you can face this challenge later if you're not up to it now.

A saved game, or a Lloyd's Beacon? Because iirc, I can go between the 2 sides at-will. I'd rather wait until I'm at a higher level, so I can get through them without too much risk of death.

Those locations were visited and beaten by MM4 players long before Darkside of Xeen was released. They won't be very challenging any more if you return after gaining lots of levels on the dark side.
If you keep a save you can reload it after beating the game and check if you became skilled enough to do those lava locations with a level 20 party.
One advice: Training to high levels gets very expensive later in the game, so if you have money left take it to the bank.

Decided to give Dragon Cave at try before going over to the Darkside, and its not as bad as I thought it would be. More resting than I'm used to, but its kind of a necessity if I'm going to complete it.
Now Volcano Cave...although I did manage to fight my way to Shrangri-La, I wasn't able to "complete" the Cave by doing the skulls. Or at least, I wasn't able to when I last tried, which may have been a couple Levels ago. So after Dragon Cave, I'm gonna give Volcano Cave another shot.
Thanks for the encouragement. :-)
EDIT: And I made it through both at Level 20, then "Found Shangri-La" and got rewarded with "+1 Level" to make it to Level 21.