[Ironhawk]

Wow, what an awesome starting position! Its like getting the defense bonus of a water-nation, without the hassle of being a water-nation. You should immediately kill off any land neighbors so you can begin enjoying having all that uncontested space to yourself.

As for how to get to the mainland: the suggestions given above are fine. You shouldnt have too much trouble establishing a beahhead with one or all of them.

My concern is how you will transport your regular armies from your production base (the island) to the front (the mainland). The first thought that comes to mind is: isnt there an item which gives a commander sailing? Not the flying ship, a different item, which confers the regular Sailing ability. If not, I would suggest you research Gateway and then have a heavy astral mage move key troops to the mainland via that spell every couple of turns.