Hollow Knight

The last of the Dreamer trophies, Monomon the Teacher can be found in Fog Canyon in the Teacher's Archives. At first, the Fog Canyon cannot be fully explored, due to the shadow gate blocking it off. There are two ways you can get to the other side of the shadow gate, the first is by getting the Shade Cloak which is found in The Abyss and dashing past the shadow gate but this requires more effort as it requires going to Kingdom's Edge, defeating Hornet a second time, getting the King's Brand, going to the Ancient Basin, going into The Abyss and finally getting the Shade Cloak. The second method is a lot easier, which is simply to get Isma's Tear, located in the Royal Waterways. Once you've acquired it, there is a section in the Fungal Wastes which cannot be accessed as it is flooded with acid. With Isma's Tear, you can swim past the acid and access the other side of the Fog Canyon.

Once you have explored the Fog Canyon's other side, you will come across a large building with Quirrel standing outside of it. Once you enter, and explore deep enough you will be met with a boss battle against Uumuu, a jellyfish like creature. It is impervious to damage at first but Quirrel will come in to help you. His nail attacks will burst Uumuu's membrane, leaving it vulnerable to attack. It's attacks include creating several balls of electricity around the boss room and balls of electricity that will follow your movements. The first can be dodged by finding a space which doesn't have a ball of electricity and the second can be dodged by going around the boss room using the platforms provided until Uumuu stops. Keep dodging its attacks until Quirrel comes in and attacks it, in which you can attack it. Once it's finally defeated, you can proceed with the Teacher's Archives until you find Monomon sleeping in a water tank. Quirrel will come and unseal her tank, allowing you to use Dream Nail on her. Attack her spirit and hold to absorb her essence. Once the seal is broken, you will receive this trophy.