Hexen II is described as 'The Hammer of Thyrion project is a cross-platform source port effort of Raven Software's Hexen'. There are more than 10 games similar to Hexen II for a variety of platforms, including Windows, Mac, Linux, Steam and Xbox. The best alternative is Half-Life. It's not free, so if you're looking for a free alternative, you could try Unreal Tournament or Cube 2: Sauerbraten. Other Hexen II like games are Doom (Paid), Quake (Paid), BioShock (Paid) and Warsow (Free, Open Source).
Half-Life is a science fiction first-person shooter video game developed by Valve Software, the company's debut product and the first in the Half-Life series. Represent entire series of Half-Life games including Half-Life, Half-Life 2.
Doom is a science fiction horror-themed first-person shooter video game in which players assume the role of a space marine, popularly known as "Doomguy", who must fight his way through the hordes of invading demons from Hell. Represent entire series of Doom games including Doom , Doom II: Hell on Earth, Final Doom, Doom 64, Doom 3, Doom (2016), Doom Eternal.
Quake is a series of first-person shooter video games released by id Software. In the game, players must find their way out of various maze-like, medieval environments while battling a variety of monsters using a wide array of guns. The successor to id’s... Represent entire series of Quake games.
Warsow is a completely free fast-paced first-person shooter (FPS) for Windows, Linux and Mac OS X, set in a futuristic cartoonish world where rocketlauncher-wielding pigs and lasergun-carrying cyberpunks roam the streets.
Freedoom is a WIP a complete free content game based on the Doom engine. It's not an engine, but it's replacement game data with entirely original content, Compatible with a majority of game mods made for Doom. Comes in Three Flavors~.