The 4E Greek Mythology Campaign: What Makes it Different?

I think it's a valid question no matter what system you are using. Every RPG comes with some implied setting and fantasy RPG's come with more than most. Whether it's D&D, Runequest, or Mazes and Minotaurs most fantasy RPG play involves running around with swords and magic and fighting monsters in moderate to high amounts. What makes a Greek Mythos game different?

1. The look and style of the game: yes in many ways it's the least important thing mechanically but since a lot of these kinds of games take place in the imagination it might be the most important difference of all. Whether it's using greek names for characters, using historical names for cities and towns, using the Olympians for the religious angle, changing up some of the equipment, or making everyone watch Clash of the Titans before the first session, there are ways to promote the different look and feel of the game that makes it feel different from a traditional medieval fantasy RPG.
2. The monsters: Yes, there are hydras and chimeras and harpies and giant bulls and boars and scorpions but there are not huge armies of orcs and goblins, no scheming dark elves plotting in the underdark, and no fire-breathing dragons holding princesses hostage. A greater portion of the monsters running around tend to be regular animals grown to huge size or otherwise made more terrible. Others may have been mortals cursed by the gods. Others make no more sense than a lot of D&D's original creations but they have a history in the real world that runs deeper than the beholder or the flumph. Terrible opponents tend to be single mighty foes rather than hordes of lesser creatures. In old school terms the "No. Appearing" tends to be "1-4" a lot more than "40-400"
3. What is done: There is not a lot of dungeon crawling in Greek Mythology. There is a lot of questing, by land or by sea. So we will be spending less time invading underground complexes (though there will be some of that too) and more time roaming the countryside and deposing tyrants. Jason and the Argonauts is one of the archetypal group quests and it's a major model for the game. If someone gets politically minded then there's an option to try and unify the Achaean city states or maybe just take over one of them and rule it themselves. There are a lot of options in the campaign but it's not a megadungeon game and I'm fine with that as I'm working on that separately anyway.
4. Divine Intervention: Unlike most D&D games and unlike most other fantasy RPG's, the gods in the Greek myths make regular personal appearances to heroes. That will be the case in this game as well. Each character will likely develop a relationship with at least one god (it may be a part of character generation, still working on that angle) as all of the heroes in the myths are either descended from or favored by at least one deity. They also tend to be opposed by at least one deity and that will be fun too. Hera is a common nemesis goddess but I'd like to branch out some. 
5. History: I've thought about setting the game in a made-up not-Greece with made up not-Olympian gods but that kind of defeats the purpose of running it. I'm using real maps of Greece with the real cities and some of the real heroes and history of the region. Now I'm also contemplating Centaurs as a playable race so it's not all about the history here but it's still different than playing in Greyhawk or the Realms or Glorantha. These are and were real places and that puts a different flavor in the game. Being a bit of an armchair historian this scratches an itch for me and sets up a lot of potential games using the same mythic history with Egypt and Rome and others down the road. 

The major concepts of this campaign are:

• The first age of heroes ended shortly after the Trojan War which was about 100 years ago. Since then no new heroes have arisen and Achaea has fallen into a dark age with travel and trade decreasing and national unity a thing of the past. Monsters and marauders roam the countryside, making the situation even worse. This both sets up the "points of light" background for D&D and is pretty much historically accurate as far as is known.
• The Olympians are not the only gods in the world and they did not create the world. The titans were the precursors to them, and there was a set of godlike beings prior to them that the titans fought in ages past. This sets up some mysterious history ad lets me use the titans as sources of information about these older powers so that they are more than just enemies. Some of the pre-Olympian gods historically are earth deities and are referred to as Cthonic gods - I'm thinking of making them literally Cthonic gods which allows me to drop mindflayers and other tentacled things in if I feel inclined to do so. I think "Brain-Eaters" sounds a little more exciting than "Lotus Eaters" for a D&D game. 
• Worship of the gods has decreased as civilization has crumbled. Various lesser powers such as demon princes have started to creep in through the cracks and secret cults have sprung up here and there. The gods are ready to expand their influence again and stamp out these others, and they are ready to choose new heroes to do it. 

The divine element means that there will probably be an extra conversation with each player about what power they would like to be associated with at the start of the campaign. that's OK, that's one of the reasons we're playing this one, to make it a little different from standard D&D.

So how will the campaign start? I will start it off in central Greece near one of the major cities and give the party several rumors to investigate. Among them will be some abandoned shrines, some ruined settlements, and perhaps a frog-demon cult that needs to be dealt with. I plan to use Bullywugs as the opponent in this as they are both nicely diverse in 4E with multiple types and a good low level race I have not already used which is refreshing to both the players and the DM after months of kobolds and goblins. I know frog demons aren't exactly historical Greek but when it comes to low-level monsters I want something that's not one of those common D&D starter horde creatures and these fit the bill pretty well.  I am open to other ideas if anyone wants to chime in.

So it is Greek-flavored and Greek-centric but it is not strictly Greek-only content. I will deliberately keep out certain races and creatures that shift it more towards a medieval flavor (Elves, Dwarves, Crossbows, fire-breathing dragons sitting on gold hoards, Knights, Fey creatures and races) but things that are not tied to a certain historical period might be included. This could be things like Beholders, Undead, traditional D&D style arcane magic, and frog-people.

Anyway that's my rundown of why I would run this game. If it isn't any different then there's really no point to doing it. So hopefully I will do it right enough that the players will have a good time with it. We will see.