By winning more ground, a heightened sense of power and leadership takes over the militant group and they not only gain residential areas, they might own stretches of deserts or barren land. When they gain a residential area or part of a country what follows is utter bloodshed, destruction of property and mass killing of people whom they term as disbelievers.
The power and control of the caliphate of ISIS is growing rapidly and surely. As they grow into various parts of the world like a creeping cancer, the group is also becoming highly dangerous. It is not just a terrorist group, they claim to change the world order and system to that which was prevailing 100 years ago. Recently after taking over Mosul, the leader of ISIS Abu Bakar Baghdadi claimed to have changed his name of Caliph Ibrahim and that the state of Syria and Iraq were under the control of caliphate of ISIS.
The basic and foremost requirements of a caliphate are mass territorial ownerships and this is what ISIS currently aims to do. The trail of terror that they are slowly leaving all over the world is extremely dangerous.