Icon of Sin/Doom II RPG

The Icon of Sin is the last boss of Doom II RPG towards the end of the game. He is the creature that corrupted VIOS.

Background
After defeating VIOS, Stan Blazkowicz, Kira Morgan and Riley O'Connor are able to reach the Icon of Sin on the back wall. After a carefully placed rocket blast the Icon of Sin is destroyed.

As the Icon of Sin turns to rubble and dust, the evil presence you've felt dissipates. Though VIOS has been destroyed, you sense that elsewhere other battles are raging. You may have won this battle, but the outcome of this WAR has yet to be decided.

Behind the scenes
The nods to 'other battles raging' and "WAR has yet to be decided" is likely a reference to Doom I and Doom II, Final Doom, and Doom 64.