A creature hit by Faerie Fire sheds light and grants advantage to attacks against it, it also cannot benefit from being invisible. ... Pairing a spell-like Faerie Fire with this ability gives the rogue a huge advantage by effectively giving them the opportunity for sneak attack on all of the affected creatures.

How does Faerie Fire work?

Each object in a 20-foot cube within range is outlined in blue, green, or violet light (your choice). Any creature in the area when the spell is cast is also outlined in light if it fails a Dexterity saving throw. For the Duration, Objects and affected creatures shed dim light in a 10-foot radius.

Does Faerie Fire remove invisibility?

Fairy fire cancels all benefits of invisibility and grants advantage if the attacker can see. So being blinded or fighting in magical darkness still gives disadvantage for attacks that is not cancelled by fairy fires advantage.