For those who don't know: Discord is a server-based communicator that contains the functionality of IRC, Skype and Teamspeak. Each server can have any number of text and voice channels, with various permissions on user or group basis. The link above points to the main Discovery server that I set up when this communicator surfaced, however you should make your own servers for your factions.
One example of such functionality is setting up a server for the entire NPC faction and adding channels and groups with permissions for official/unofficial faction members.
Discord also supports its own version of @mentions, which will alert you each time someone mentions you or mentions @everyone. It is a useful feature for emergencies and so on.
It has clients for Windows, OS X, Android, iOS and browsers.
I'm sure it's neat and superior and all, but my reason for sticking to Skype is mostly inertia, because most of the people I talk to continue to use it.
I still wholeheartedly prefer Discord over Skype after testing it out with a few buddies some while ago.
But the truth is as Rodent had said before. People are still using Skype mostly, even if all the differences are apparent.
It's the same for me to be honest. I continue to use Skype only because others do. Even my closest friends.
It's a tad bit sad at the same time since I actually wanted to switch to Discord for a long while. But now I've stopped using it again because we're still sticking you-know-where.