Yes.

Pandamonium event is a uber character thing only. No hybrid or poorly built character could hope to survive in those areas, partially because of the immunities and the high amounts of HP for enemies.

Essentially, what you do, is do a bunch of Countess (Black Marsh's The Tower), Summoner (Arcane Sanctuary), and Nihlatak (Halls of Vaught), which drop the three keys, Hate, Destruction, and Terror keys. after synthesyzing them in the Cube, you get to fight an uber boss, Litith (Andariel palette swap), Uber Duriel (Hell palette), and Uber Izual (normal colors). They drop the Brain, eye, and Heart of the three Brothers. When the organs are synthesized together, they lead to Uber Tristram, where you fight Uber Mephisto, Uber Baal, and Pandamonium Diablo. The last one that dies drops a Torch, a Large Charm with random +3 skills to a certain class, and random + attributes, and random + resistances.