You get an achievement. that's pretty much it.
There are 13 campaign skulls ( 9 gold ones which unlock achievements and 4 silver ones which make the game more fun ) and 6 mythic skulls ( 3 for the halo 3 mythic pack and 3 more for the halo 3 odst mythic pack )
if you want to know where the skulls are all you have to do is go to youtube and put in "halo 3 odst mythic skulls" and it will show you how to get to them
the same way in halo 3 because when you play halo 3 mythic it says your playing halo 3
Yes, halo 3 mythic is the exact same thing as halo 3 just doesn't have the campaign, also Halo 3 mythic has the new mythic maps included. Online will not change during any gameplay.
archon armor
they come out with the halo 3 O.D.S.T game
You can't. The Mythic Maps our only playable on Halo 3, not Halo Wars.
It doubles the health of enemies
no
Mythic map pack mythic mature pack
No. You either need to purchase it from the marketplace, or you can get the mythic disk when you buy Halo 3: ODST.
All of the maps, including The Mythic map pack 1 and 2, come on the Halo 3: Mythic disk that is included with ODST. If you don't want to buy ODST, I believe that the full Mythic maps are available on Xbox Live marketplace.