Machinery of War Quest/Spoiler

Required Equipment

 * 37 Bricklayers' Kits (About)
 * Fire Bug

Method
Go to Baxter, he is outside Thais Castle.

Ask him for "Orc War", and he will tell you that are a couple of different things you can do, 3 of them.

First is to repair and maintain Outposts, second if to put Orc War Equipment, such as Catapults and Siege Towers on fire. And the third is to find their war plans, however they know the current war plans so always ask Baxter for "War Plans" before going to look at them.

Outposts
Buy 37 (About that is needed) Bricklayers' Kits' from Baxter. Go to the Wyvern Nest Outside Orc Fortress.

I recommend you going Wall 1 -> Wall 2 -> Outpost 3 -> Outpost 2 -> Outpost 1 when repairing, just rush, just make sure the orcs spawns (mini raid) at every place (That means you fully repaired that place).

This image will help you to locate the walls and outposts.