This game is quite awesome! Do not be fooled by its Early Access tag, This is a far more finished/polished product than hundreds of others being sold as full games on Steam.
You progress through levels of increasing difficulty and different baddies. In some levels your objective will simply be to @KILL THEM ALL!@ while in others you'll also have to complete some other task in the towns.
Your Necromancer (Nekro) class determines your playstyle. There is a brawler, grenadier and ranged Nekro, all with different skills and powers.
They all however have one common theme, which is summoning. You can unlock 10 different types of summons and each of these has a variant that you can switch between on the start of a level to tweak its abilities and attacking style. This allows for a surprisingly deep range of compositions as you can tweak your "army" to match your abilities and complement your other summons, and you can do so differently on each level.
The Nekro himself is relatively fragile so you'll need to manage your minions well. Deciding where to spend your early points of summoning resource (you use blood collected from corpses/enemies) and which ones to prioritise summoning in order to face the first sets of enemies and start adding more units to your army ia pretty awesome and makes you strategically try to plan ahead.
Even when you've reached the "peak" of your power however and have summoned 10-15 units, you still need to manage the enemy groups carefully with your skills and by prioritising targets, because if your army targets different enemies in a large group you'll find yourself without summons and running for your life very quickly.
All in all this is an incredibly fun little game, and is well worth the asking price imo even if it's in Early Access, which I usually stay far away from as it's such a gamble.
One last thing I want to note:
The developers aren't afraid to completely overhaul systems and parts of their game in order to make it more fun and interesting. A lot of the points I mentioned above were only introduced in the latest patch, and improved where the old game had some big problems with balance and being able to manage summons/enemy aggro. However the devs have made bold and frankly quite big changes to the overall game which have made a huge difference and are a great improvement on the original Early Access release.
I'd give this a solid 8/10 (before the patch this would've been a 6). Keep it up guys, eager to see how good it'll be when it's out of Early Access!