Since adepts keep a distance (usually about 4 tiles), as a knight try to trap them in a corner and kill using Heavy Magic Missile or Explosion runes when they turn invisible. Be careful while trapping him, because you might lure more cult members on yourself (they rarely appear alone). As a paladin you should lure single adept (for easier and safer killing) and kill shooting bolts with help of HMM runes whenever they go invisible. Easiest way to hunt them with mages is to summon Demon Skeleton as a blocker. All adepts' ranged attacks are life drain type, which won't affect Demon Skeleton. Just lure adept on your summon, and kill him using any runes. Keep in mind that if you start attacking with wand, summon will follow adept which may lead to luring more monsters - try to make your summon stand still. Watch your hp carefully, and try to heal whenever it drops lower than 350 - adepts can deal some nasty combos with some additional damage from summons. Don't kill ghouls he summons, rather focus all your firepower on adept. Don't forget about Dwarven Rings, being drunk is something you want to avoid if you need to run. Having a few area attack runes might be good idea if you'll have to face more cult members. Also, bringing one or two Garlic Necklace might be a good idea since their Life Drain can reduce your HP rather fast.