I used up my 20 stamina on dark dungeon then finally founded the level but when i killed him there was only a tier 11 helmet no power stone or dark sword?

NIGHT GUES

I used up my 20 stamina on dark dungeon then finally founded the level but when i killed him there ...

Well you're not alone. That happened to me a lot of times before... until I'm fed up with it 😅😅. It is extremely rare to drop that's why I'm not surprised. Besides I already got one.

My progress in stages is stopped at last level of ancient forest of hell mode .even not getting a item of higher then rare in draw

If your progress suddenly hit a brick wall, then upgrading your equipment is the solution. Try collecting as much stones necessary to upgrade and play rounds you have finished like main bosses cause it drops more items than normal ones. One way to complete the game is to clear every stage with 3 stars and play sanctuary to unlock your allies.

You don't need to rush things just to get to higher levels cause you will get there when you are ready.