The Moon Grotto is an area in Nibel. It is located below the Thornfelt Swamp.
Ori and the Blind Forest/Definitive Edition
Moon Grotto is first introduced while chasing Gumo, marked by the large letters, the lasers, and the change in music, switching to a sad clarinet tune. The spikes here will often hurt a lot, taking up to three lives. Moon Grotto is also quite hard in general, with many secrets and side paths. For the lower part of Moon Grotto, see here.