The BFG in Doom is actually something you can’t miss but there is a puzzle attached to it that might stump you. There is giant laser trap that you need to get through in order to access the BFG. Check out this guide to figure out How To Get The BFG In Doom!
How To Get Past The Laser Trap In Doom
You can find the BFG in the Lazarus Labs mission. As you progress through the level you will eventually come to a container that is locked and inside is your BFG. When you enter the room with the BFG there will be 4 ledges you can jump up onto with green lights. Use the switch in the room to activate the trap and jump onto one of those green light ledges. The floor will disappear and down below there will be a laser grid that will kill you if you die. Wait for a laser grid to come up above you and the BFG. If you look under the laser you can see red lights all over it. Shoot a few of those and the laser will drop and you can jump to the BFG.
The BFG cannot be upgraded(not that it needs it) and the ammo is really rare. You can sometimes find a shot or two in a big fight but for the most part you are going to want to save your shots. The next room has a ton of enemies to use it on so give it a go just so you know how it works. Shoot above or in between enemies because once the blast hits a wall or target it will stop traveling and stop killing.
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