I am currently DMing a 5e homebrew campaign, and I was looking at the Drow monster stat block.
They have innate spellcasting abilities and one of those spells is Faerie Fire. In the description, it states that the targets must make a Dex saving throw or be outlined in color.
How do I determine the DC that is needed to pass the Dex saving throw against the Drow's Faerie Fire spell? It is not stated, and I am just a bit confused as to how to arrive at this number.