Things You'll Need
Instructions
Standard Tactics
Clear the level and obtain the four scepters you need to release the demon.
Rest up and memorize spells of all four elemental types. Have wizards prepared to cast elemental damage spells, and druids ready to summon elementals and shape shift into elemental forms.
Buff your party. Use protection against evil as well as gear or buffs that protect against elemental damage. Don't forget your standard buffs, such as stoneskin for wizards and sorcerers and ironskin for druids.
Summon up Mordaiken's swords, devas and other minions and position them close to the demon's cage to soak up his initial attacks.
When you release the demon to start the battle, pause the game to determine his form. You can kill him quickly by using the elemental damage to which he is most vulnerable. His red fire form is vulnerable to cold; his green acid form is vulnerable to lightning; his gaseous lightning form is vulnerable to acid; and his ice form is vulnerable to fire. Make sure to switch your damage type as he switches forms.
Thief Tactics
Set seven traps just outside the demon's cage.
Hide in shadows as another member of your party releases the demon.
Backstab the demon. You may need to run to a library and hide again for a second backstab if you have a fairly low-level party, but normally the traps alone will get the demon below half-health, and one backstab plus any damage done by other party members will kill him.
Poison Strategy
Close the lower door to the poison laboratory and turn off the fan in the air laboratory.
Buff your tank and equip him with "Boots of Speed." Make sure to have poison resistance gear or buffs on your tank.
Move all other party members out of sight of the cage into the fire or ice library.
Use your tank to release the demon. The tank will need to "kite" the demon. Kiting means running ahead of the demon, keeping it close enough so that it will follow you but far enough away so it can't actually hit you. Kite the demon into the air library and then into the poison lab. When the demon is past the center of the poison lab, run your tank out into the air library and shut the door to the poison lab.
Wait for the poison to kill the demon before opening the door and running in to loot his body.