I've been playing the campaign for a while, but I just hit an odd snag. I fought a depressingly short battle for the last free shard in the astral map, lost... and now there are no free shards at all. I'd invade one of the masters' shards, but the only ones left are Masters with whom I have good relations (and one guy I just met and don't want to fight yet), and so I'm reluctant to do that.

I'd always assumed that advancing the turn in the astral would bring new shards like a turn spent in a shard battle does... but that doesn't seem to be the case. So I'm just pushing the button, accumulating energy, while nothing happens.

So is my only choice to invade one of my friends? Or has something gone wrong?

What astral turn is it and what difficulty?

But, probably, you are on the way to lose.

Still my first campaign, I'm playing on Beginner. And doing the math on how much energy I have now, I think I was around turn 45 or so. But then I just kept ending turns for a while waiting for something to happen. Got Zarr's warning on turn 70. So I went ahead and invaded the dragon master who'd popped up, banished him, and now I'm on turn 71. Of course now a new shard appears.

Sigh.

Is there like a maximum combined number of shards and masters' worlds that can be on the map at a time or something?

Everything here: http://www.gog.com/forum/eador_genesis/how_long_is_the_campaign/page1

There is no limit on amount of shards, but you need to go through quests.

Well I'd just destroyed Ul-Dagan and gotten the quest to help Erdu build his device... but then I was left with no free shards on the astral map, just masters. I was ending turns in the hope that new shards would appear for me to work on.