As we all know, Theros block is based loosely on Greek mythology for its flavor themes, about to the same extent it is based on enchantments for its mechanical ones. It tries to take a kind of loose outline and go in new directions with it. That being said, there are definitely plenty of cards in the block that are direct adaptations of stories from the source material, and there are plenty more where those came from to make for cool top-down cards in Journey into Nyx. Here are some of the most likely unused ones:
- Hercules. The 900-pound gorilla in the room - and not just in terms of appearance - is the most famous Greek hero of all, the Son of Zeus renowned for being the strongest man of all time, his impossibly difficult Twelve Labors, and his sheer tenacity. There was almost a Hercules-based card in Theros - a legendary Human that cost 2RR and was a 12/12 that couldn't attack or block unless you controlled twelve or more permanents - but this was scrapped because it felt wrong to have a mere Human, demigod or not, be the biggest creature in a set full of monsters. That said, it'd be criminal if we didn't see this reference made, although I'm disappointed it's not with the Labors-flavored card.
- Atlas. Now here's a fitting biggest creature. The Titan named Atlas was made to hold the heavens separate from the earth as punishment for his rebellion. The art of Titan's Strength does sort of hint at him, but is mostly a reference to Sisyphus, and it'd be a heck of a twist if Nyx were held aloft by a missing red and green god who was cast out by his fellows.
- Daedalus. We have Icarus, the reckless boy whose broken wings killed him, in Impetuous Sunchaser, and sort of, at the same time, Phaethon, who has a similar story, but not Icarus's relentlessly inventive father, the man who designed the Labyrinth that kept the original Minotaur trapped, as well as the aforementioned working wax wings, a huge brass Golem named Talos, and many more things. He'd definitely make for a legendary creature that's all kinds of cool.