|Signs of nearing||Quotes (voiced by BlueCatRiolu)|
|Theme song|| The Second Malformation of "G"|
Shadow Riolu is a boss on Slender Fortress.
Shadow Riolu is Riolu's evil clone created with the G-Virus. He has a large bloodshot eye in his right shoulder.
A scientist was examining a blue kitten that died after birth. The kitten looked like Riolu. The moment the man left the room, a G-Virus fell and pierced the dead kitten's arm. Causing the kitten to grow to a full-grown cat, and creating a huge bulge in his arm. A huge red eyeball opens up in his arm, and the cat opens its red eyes. Shadow Riolu has awoken as he leaves the scientist's office.
In Slender FortressEdit
Shadow Riolu is a regular and normal chaser at the beginner, the longer he chases a person, the faster he gets, although he has a very long range using his mutated right arm, it is almost impossible to outrun this range and how fast is it, the mutated arm deals almost 20 damage per hit, but he hits like pretty fast, faster than almost most bosses, the stun is almost pretty useful to outrun him so have your time stunning him, as the stun takes his sanity for 3 seconds to outrun and flee from his sight.