So I downloaded the Grim And Somber ENB:Jyggalag and everything looks great. However, the fire is too bright.

http://s1027.photobucket.com/user/paladinofthelantern/media/WTH%203_zps5vapp7aj.jpg.html?sort=3&o=1

Any suggestions?

I'd ask the mod author. Make a post on the mod page at the Nexus.

Light effects, if the meshes have the correct shader properties (and they don't always), are controlled by the [ENVIRONMENT] section in enbseries.ini. The two variable types you're looking for are PointLighting and ParticleLights.

Curve values adjust the contrast, higher for more/harder contrast (and color warmth), lower for softer lighting with less contrast and warmth. Generally you just tweak the Intensity values for the time of day you want to alter. You may need to slightly tweak the Curve if you make big changes. Usually a few tenths, like 0.2 or so, will make a pretty big difference for any of these values.

You can edit the file with a text editor like Notepad++, or use the in-game GUI, which is usually launched with SHIFT+ ENTER. Hit the '~' key to bring the console up first, otherwise as you're moving around the mouse, your character and the camera will continue to move while you've got the GUI open.

I would start with PointLighting, and if that doesn't do what you want, revert then try ParticleLights.

Make a backup of enbseries.ini before you make changes.

For Example: