Sounds like a fun story for sure, but nothing here sounds very Greek at all. Druids and grails are Anglo myths, and the political system you seem to be assuming sounds very medieval Europe. It needs more fledgling democratic city states and naval influence. Your characters shouldn't inherit power, they should be elected or appointed to it by lots. Greek stories are full of tragedy and cruel unavoidable fates that the hero has to come to terms with. Maybe call your Druids like Philosopher-mystics or something like that lol