When one seldom uses the CLUAetc. to bump the experience....does the game make it harder by putting harder foes in your way or is it just hack and slash all the way?

I think some areas are scaled up to the player's level, for example mummies become greater mummies become liches or something.

Just curous since i beeeeped my partymembers to 40th level in a trial run...it´s not that much fun to play without the eager waiting for the next level...but when I ran into a Lich in the shadow dungeon I figured that there might be serious trouble ahead
Especially when the twised rune are on the scale

No, monsters are not upgraded to suit the character level. Encountering Liches through every door is not very fun, or exciting.. The SoA campaign is suited for characters from level 7 to in the early 20's.

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Monsters don't get upgradede but some encounters are - for instance, in the Planar Sphere a low-level party will not meet Iron Golems in the engine room - i nSpellhold there may be a Greater Mummy or a Lich depending on your level