Wow, cAPSLOCK, your post has just fired some old memory neurons in my brain...

Dungeon Master!

I've spent countless hours on this game. High school, with a classmate and friend. On an Amiga 500. We were even making maps on paper for each level. We're talking hours of non-stop playing, we didn't eat or sleep until we were completely exhausted...

I remember we used to eat those damned plant things in your screenshot, which upped our stamina/power/abilities. After we finished eating them, we went outside the room and slept (in-game) for some time and these things kept regenerating, so we could eat some more and gain more abilities. It was a way to raise your level. Also, the small squares with the symbols on top-right were for casting spells.

Those graphics were breathtaking at the time, a truly immersive experience (IIRC, the Amiga had better graphics than your screenshot -- this is probably from a PC or other computer).

Good times...