You fall unconscious dead ?

[lady black]

Sorry, lagroth, but this does have to do with who you fight and how strong you are. As nyktos told you, there is only one way to die (a monster kills you in a fight, or gives you bleeding wounds or poison that kill you just after the fight;) and there is only one kind of dead (you wake up in bed after "falling unconscious", minus 30% of the experience points you had at your current level.)
Since this is happening time after time, you are in an area too strong for you. You do not give your stats, and did not answer the question of what killed you, so we can not give you specifics, but I suspect that you are in the Iqhan cave. Some of those monsters can cause over 30HP of damage in one hit and well over 50 in one turn of combat in a second or two, leaving you dead and wondering what happened.
You need to go to an easier area and get stronger before you go back for revenge. If you have not died until now, "after more than 20 levels," you are to be congratulated, but you are now simply being killed by whatever monsters you are fighting. You never have a chance to see exactly how you died, you just wake up in bed.