This is an awesome concept, you did an amazing job with it. I always thought the celts would make for a great addition to this game. I even thought of some godpowers specificly for the celts. You can borrow them if you like them. It goes like this:
Archaic age:
Wild times: Spawns six wild animals near the casted upon woods. They behave just like the animals of seth.
Family extension: Expands the population capacity of an house by three. (Cast on houses only and non stacable)
Whispers of the wild: All herdables are revealed for 5 secounds.
Classical age:
Transformation: Transforms an human unit to a mythical unit of the respective age the player is in.
Skilled workers: Up to four workers can be upgraded to craftsman. Craftsman build and gather faster then normal workers. (Classical age: 5%/ Heroic age: 7%/ Mythical age:10%) (Lugh would be the perfect god for this, if he wasn’t a major god)
New beginning: Spawns a little mount of gold (200), five trees and three deer in a little circle.
Heroic age:
Famine: All food production of the enemy is put on hold for 15 secounds.
Murder: A murder of crows decends and deals heavy damage to enemy units. Not effective against buildings though.
Woods of madness: Spawns a medium siced forest of black trees. The trees are few and far in between. If the enemy travels or fights in these woods one unit after another is slowly driven mad and attacks everything nearby. Friendly units are safe, but if a worker stumbles in them and stays to long he transforms into a wolf, attacking everyone. It also can’t be casted over an building and no building can be constructed in them.
Mythical age:
Acid rain: Deals great damage to enemy units and buildings.
Ominous fog: Thick mist that disrupts the enemys ability to see what’s happening. The enemy can neather see or control his units until the fog has subsided. Lasts for 25 secounds.
Awakening: Spawns a great animal statue. If inchanted by a druid for three minutes the statue awakens and can fight for you. The statue is one third as strong as a titan.