Hub 1: Bright Crucible

Bright Crucible is the secret level of the first hub in Hexen.

It is accessed at the end of the hub.

''Other horsemen have attempted to conquer worlds only to be defeated. Here in deadly radiance lies the heart of d’sparil, first of the serpent riders to fall in battle.''

Walkthrough
This level may be a little difficult due to all the monsters that are there, namely a lot of Chaos Serpents in a big opened area - killing them, especially if you’re a Fighter without ranged weapons, is a bit tough. But the "puzzle" part of this level is pretty easy. It goes pretty much like this:

You appear on a platform with pillars all around you. Kill all the monsters that bother you and then jump off this platform either to your right or left (either of these parts can be accessed from the other by jumping across a small gap on the southern end of this area), on the grassy ground below you, again killing all the monsters as you go. Now on northern end of both of those areas, there are high platforms with a lift that can take you there. Go first to the western one of those two. On the platform, there are some ettins and stairs that take you to a corridor. When you step in there, a lot of rooms open all along the corridor, releasing some centaurs. Kill them and go through the corridor until you arrive into a room with fireballs shooting from the statues in its corners. In the middle of this room, you will see a red, gem-like object. Take it (it is the heart of D'Sparil, the final boss of Heretic) and the fireballs will stop. Then go take the other lift to the platform on the eastern part of the level. There you will find a corridor similar to the first one, again with all the rooms opening and releasing ettins this time. Kill them all and go to the end of it, where you will find a painted window. Break it, behind it is another room with fireballs shooting all around. In the centre of the room is a pedestal, where the heart of D'Sparil belongs. But putting it there doesn’t happen automatically, so you have to select the object in your inventory and use it. As soon as the heart is at its place, the fireballs will stop. Now a big flight of stairs has risen from the big pool of mud on the south of the level, going all the way to the (otherwise inaccessible) platform where you have appeared. Get there and behind it, to the north, you will see that even more stairs appeared, leading into an area with some monsters and goodies (mostly ammo, quartz flasks and - on higher difficulties - an icon of the defender). When you’ll be through with that, take the big stairs down into the pool of mud and go through it further and further to the south (beware of stalkers). On the end of it, invisible stairs take you down to a small mud-corridor that leads into a room with a portal back to the Seven Portals. At the mouth of this cave is a linedef which is the first of the two triggers which opens the secret door on the Forsaken Outpost.

Trivia
"Crucible" in this context means "severe test or trial", one of many archaic usages in Hexen.