Alright, so I`m home so I had access to all my old D&D books, I went through my AD&D monster manual and knocked out a list of possible Legendary Creatures. Some of the entries on this list are consolidated groupings of similar creatures. Feel free to let me know if you I think I missed anything.
Giant Blob, Ooze, Slime
Giant, Ettin,Cyclops, Titian,
Giant Gar,Giant Fish
Deamon (Any big demon or devil)
Giant Worm (Purple Worm)
Giant Spider, Giant Scorpion
Greater Shambling Mound
Giant Squid, Kraken
Wyvern (Probably stick in with Dragon)
So yeah, I`m going to break this list down into individual entries and go from there.
(I`m watching Jurassic Park 3 right now, very inspirational).