You play as a king that must build up his castle and fend off the on coming attacks from monsters of the unknown, use archers and knights as well as huge walls with tall towers to defend your keep from the dangers that lurk nearby. Basically its a rolling tower defense + expansion, you use farmers to gain more coin to hire more beggars to join your ranks and help defend or build up your walls. you even get catapults which is a cool touch, every day that passes the waves get harder and bigger (excuse the pun).
Just be careful, if your peasants aren't protected and the monster bash into them then the monsters will knock them out and steal their coins, which returns them into what they were once... Beggars.
Yes truly this game gets a 8 - 10 on the LoG games list really worth the buy even in its early stages of development (remember to opt into the open beta via Steam settings)