A distinctive feature of Hexen are very deep pits, which make the player fall a loong way and die instantly.
Well it turns out in Vavoom you can survive those falls. Jump into a wall limiting such an abyss and press forward. You may want to try different angles and positions, but it's possible to survive falls in Guardian of Fire (at Flame Mask) and at the end of Seven Portals, taking 0 damage. It works most reliably when you run into a wall while looking down (at your feet), or in corners of rooms
This is likely to affect other games as well considering the engine is similar - but Hexen suffers particularly from it because it's the only game which implements falling damage. I don't know, perhaps Strife has "bottomless" pits as well.
Later i tried it in current version of Doomsday Engine, and the same falls are always fatal. I can't slow my vertical fall by tweaking my movement, position (corners), or perspective angle.