Welcome to the walkthrough for Dungeon Master 2.
To your right you can find all the maps which include all the locations of the items and help you with all the puzzles you might face.

From a story perspective however i'll explain what needs to be done here.

You start out as one hero. Torham Zed.
You will need to pick 3 other heroes to accompany him. As 2 people will stand in the front to take the hits. Its best to get 2 strong fighters. The rear should be where your priest and wizard are. But the choice is yours.

Once you get out of the cave you will find yourself in a village where you can supply your heroes with weapons, armor, food and whatnot.

When you venture out into the wilderness you will come across the Skullkeep Castle.
It shows an unlocking mechanism which requires 4 clan key parts to open.
All Clan Key parts are found in different areas:
The Area of Lightning
The Area of the Moon
The Area of Energy
The Ancient Temple

Once you acquired all of these parts you will enter the castle and find yourself a new objective.
You will need to enter the Void to defeat the final boss. It is however closed by a gate which can only be opened by making the following things work:
The Boiler Room
The Furnace
The Pumping Station
The Valves Station

Once you have all of these covered, you can finally go in and get rid of Dragoth. Good luck!