There are many songs that reference cryptids or mythological creatures. Songs that are mainly about the cryptid or just mention it should be added.

Lochness by Judas Priest - Nessie

Just Leave by Paradise Oskar - Dragons, Vampires, Trolls, Goblins, Werewolves and Ghosts

Ghost by Neutral Milk Hotel - Ghosts

Little Ghost by The White Stripes - Ghosts

(Don't Fear) The Reaper by Blue Oyster Cult - The Reaper

Hellhound On My Trail by Robert Johnson - Hellhounds

Monster Mash by Bobby Pickett - Zombies, Ghouls and Vampires

Wendigo (Sung by Denise Finley) by Dwain Story - Wendigo