The Hammer

Armed with his trusty hammer, the King's Champion Gharrik Anzar is known for two things: Slaying his enemies and conquering women. 
But when a portal to another world opens in the middle of his homeland and monsters begin to pour through, he'll have a new mission. 
Step through the portal, kill everything that stands in his way, and stop whoever is sending the monsters through. 
There's just one problem. 
He can't bring anything through the portal, and the technology on the other side is… well… lacking. 
In order to win, he'll have to build an army out those he finds on the other side, outfit them with weapons and armor they've never seen before, and then march them through a battalion of undead, orcs, and ogres. 
It sounds impossible, but if it didn't, they wouldn't send the hammer. 

Please Note: This Novel contains a Harem.