Six-Eight-Two

Six-Eight-Two is a free, horror indie game created by Divinity Studio on the Unity engine, focusing around the fiction monster SCP-682, also known as the Hard-to-Destroy Reptile. The game is apparently unfinished and hasn't been updated since 2014.

Game can be downloaded here: https://www.indiedb.com/games/six-eight-two

Gameplay
Takes place in a foundation facility where SCP-682 has breach containment. You play as a Mobile Task Forces (MTF) unit equipped with an assault rifle. After you heard loud gunshots and roars, an intercom message alerts you of the breach.

SCP-682 will then appear in the map and will begin to chase you. The player can not kill it of course, and it's hard to not get killed by 682 because of it's speed, however you are able to slow it down by shooting it in the legs and also closing doors on 682, causing it to stop and tearing open the doors.

The goal of the game is to recontain SCP-682 by luring and locking it into it's acid chamber where it will then be drowned in acid via a nearby control panel.