I like the idea of doing this, it sounds like it would be cool.
For time period, you can make the Egyptians late New Kingdom, and the Greeks late Bronze Age, which puts the Greeks during the time when most of their myths were set (and further differentiates them from whatever Iron Age Greeks 0AD will have). That would make Egyptians and Greeks contemporaneous.
The Mesoamericans would be tougher, since the Olmecs started around 1200 BC, and I don't know when the Celts and Norse became archaeologically recognizable culture groups. So another option would be to set it around 1000 BC, that allows the Egyptians, Greeks, Mesopotamians, and Mesoamericans to be contemporary, and makes the Norse, Persians, and Celts more reasonable additions.
It would be neat to base the Romans off of the early Republic, before they started expanding, or even to bring in some Italic flavor from the Oscans, Sabines, and Umbrians.
Of course to some extent the time can be totally imaginary, since it is mythic, but having a good time period to base each culture off of would help keep them looking accurate instead of eclectically random.
For gaining power or favor from the gods.. oh, that makes it very difficult to use the Olmec, since their writing is undeciphered. Hm. Well, for the Greeks I'd use the 12 Olympians, and for the Egyptians I'd use the Re, Osiris, Isis, Set, Horus, Ptah, Nephthys, Anubis, Sakhmet, Hathor, Thoth, and maybe Geb, Nut, Shu, and Tefnut if you can think up what they do. Except I would try to use the actual Egyptian names for them. For some of those that I named there are linguistic reconstructions of how their names might have been pronounced in the Old Kingdom, and for all of them there's the possibility to use the standard transcription of their hieroglyphic names, instead of the Greek names I used for most of them in this post. Thus Re' or Re'u, Wesir, `Aset, Setekh or Sutekh (?), Her or Heru, Ptah, Nebet-hut, Inpu, Sekhmet, Hut-her or Hut-hert, Djehuty, Geb, Nut, Shu, Tefnut.
Concerning the North American and Pacific cultures, they should definitely be based off of individual cultures, not off of a mishmash of an enormous number of very different cultures in a whole continent or everything from Polynesia, New Guinea, Australia, the Philippines, and Micronesia combined. You can do this to some extent with Mesoamerica, which is a geographically limited group of related cultures with many customs, foods, buildings, weapons, and religious traits in common, but you can't do that with something as huge and diverse as North America, or "the Pacific." I'd say pick one culturally related part of North America, like "upper northwest coast" or "New England" or "southwest" or "Iroquois." For "the Pacific" I would say, pick something much more culturally related such as "southern Polynesia" or "northwest Australia" or "highland New Guinea" or "Filipinos." All of the Pacific is the equivalent of "all of Europe, Mesopotamia, India, and Russia mixed together" in terms of cultural and mythological diversity. In terms of linguistic diversity, New Guinea alone is probably the equivalent of all of North America.
Myth Units: The Harpies, Chimaera, Minotaur, Basilisks, and Griffins are all Greek, and in fact Griffins could also be available to Mesopotamians, Hittites, Persians, and Egyptians, since all of them had legends or images of them. They would look slightly different for each culture, in that case. If Griffins were only available to one culture, I would give them to the Mesopotamians. Also, the Harpies don't breathe fire, nor resemble lions, in any myth I've read. You might have them confused with Chimaera. Myth units that die could be summoned again from the underworld, but the whole orange powder thing is fantasy, not genuine Greek myth. I do like the idea that unique monsters (Minotaur, Chimaera, Cretan Bull, etc.) should be unique, one-at-a-time things. Arachne... I don't see her as a myth unit. She's just a woman who was changed into an ordinary spider. The Cyclopes could number as many as the Centaurs, since Polyphemos had many Cyclops neighbors.
Titans should NOT be a myth unit. While it's a common misconception spread by fantasy that they're giants or monsters, in Greek stories and beliefs they were gods, just like the Olympians. None of them except Rhea or Helios was important enough to be worth putting in the game, and even Helios had very little actual worship.
Having myth units granted by the gods seems a bit weird to me, because some monsters (such as Chimaera and Giants) are enemies of the gods, and some (such as Harpies, Cretan Bull, Klazomenaian Sow, Minotaur, and Centaurs) were sent by the gods to punish mortals, not to help them in battle.
Egyptians can have Akhu, Hierosphinxes, Kriosphinxes, Androsphinxes, Sagu, Setjau, and Set-animals, though I have no idea what they would do, only what they look like. Fire-breathing Uraei and dragons of many possible appearances are easier to figure out: they breathe fire.
Mesopotamians can have Sirrush, Humbaba, and so on. I have a list somewhere of the animal-like possibilities for each group that I could post, it would be very long though -- probably too long except as an attachment.
To Kimball: Where can I read about those Celtic mythic creatures, please? I'd like to learn more about them.
Edited by Aldandil, 28 January 2010 - 11:15 PM.