Without spoiling things too much for you, there's two game ending events that you'll need to avoid once you agree to work with the Twins. They occur around week 22 and week 60 (or thereabouts; going by memory here). However, what you'll need to do is establish a good revenue stream from taking over villages and mines (found by exploring the map), and building certain improvements at Bloodmeen (such as the Tavern). Also, you should try to keep your research going at good rate by building the appropriate structures, taking over Abbeys, and recruiting Succubi (?). These units are a force multiplier that add to your overall military strength as well as providing research bonuses.
To avoid the first gameover event, you'll need to fulfill the objectives the Twins placed upon you--capturing Raeve Keep. It's just east (right) of the starting portal immediately pass the bridge across the river. Do this after you've explored a bit and got a few villages under your influence. (Many of the starting villages are near and along the "circular" road next to the starting portal.) Bear in mind that you'll also need to have 500 gold crowns in the treasury as well to satisfy this win condition. Your personal wealth is NOT taken into account.
After gaining control of Raeve Keep, you'll have to figure out a way to gain an army to march upon the capitol in this region to avoid the second game over event around week 60. From the starting portal, if you follow along the trade road going north and then west along the river you'll eventually see a bridge going north that has an Abbey immediately on the next hex up. Just northeast of that is the "second" portal for this region; however, you'll find a hex that looks like an orc village to the northwest a few hexes away.
Starting on the bridge hex here, it's three hexes up, one hex NW, and finally one hex to the SW (or Abbey, Road, Road up, then Road and finally Orc Village hex). This orc village is actually an
orc encampment. You can find an army to recruit from here but you'll need several weeks to influence events (and there are many ways to do it) to get them into your fold.
Rastedel is found along the trade roads to the Northeast region of this map; it's large and impossible to miss. Good luck and have fun,
HaiRen!