As a Greek I alway liked computer games based in my country's mythology. Invictus is one of them although not 100% accurate as there are a lot of fantasy features (like Arachnes, a heroine never appeared in Greek mythology).
Invictus is a mix of rts and rpg genres. You begin your quest by selecting 2 heroes out of 10 (you can have 4 later) plus some warriors from different types of units (swordsmen, archers, spearmen etc or ever mythological creatures like centaurs). Each hero has his own abilities, strengths and weaknesses.
Each level is a huge map full of cities, quests and beasts to overcome. The gameplay is not something new and runs smoothly. You just have to explore each map, collect helpful items and defeat Poseidon's evil forces. At the end of each level you can purchase new warriors or update the existing ones so that you will be able to overcome the harder levels later.
Overall it's a good game. It's not something new or something that will make you go crazy but it's addictive, fun and will keep you playing for many many hours. After all, a well-made mythological strategy game for %5.99 it's a bargain, isn't it?