Abyss

The Abyss is like the Hive from Hellfire but different. The only way to get in is to blow up the entrance with the rune bomb. In Multiplayer even with the music expansion the music from Hellfire plays. In Singleplayer, the music from Diablo 2 Act 4 plays along with the hive music from hellfire.

To obtain rune bomb, kill diablo on level 16 and take it or receive it from Lester when you are a level 15 character or reach level 9.