Tomes and Grimoires are integral to obtaining the best loot possible from each mission. Against The Gain is the first mission of the third act, and sees the heroes sent to rescue captive humans from Chaos marauders. 

"Rotblood raiding parties are cutting loose in the fields around Ussingen. I don't need to tell you what that means for the poor bastards in their path. You're heading to Morgensloft, biggest farm in the area. If there are survivors - and I hope there are - you'll find 'em held captive there. Do what you can, every prisoner freed is one less slave used by the enemy. And, repay the dead in kind, if you follow..."

In total, and as with any mission, there are 3 Tomes and 2 Grimoire to collect. Collecting them all will also significantly increase the difficulty of the level, as they limit both your inventory slots and your maximum health. 

Tomes and Grimoires (In Collection Order)

1. Tome: The first Tome is easy to locate, and is at the first village you come across. Walk through the wheat field, head through the first barn, and on your left is a hay bale and fence. Jump on the hay, along the fence, and onto the adjacent roof. Immediately next to you, stuck in the loft, is the first Tome.

2. Grimoire: Once you've collected the first Tome, carry on along the path and you'll eventually reach the Orchard. To the right of the Orchard field, is a house that juices the apples. Inside the house there's an explosive barrel in the right hand corner, and a door leading down to the cellar. Grab the explosive barrel and throw it against the boarded entrance.

Once you cause it to explode, you'll be able to venture through and up some ladders. The grimoire is immediately outside once you climb up.

3. Grimoire: The second Grimoire is back on the main path as you head towards the locked barn. To your left you'll see some ladders, leading onto a roof. Climb them, and once at the top, you'll see a suspended platform on your right.

Hop onto the platform, and follow the building until you reach a dead end. Hidden behind some wooden planks is the Grimoire. ONLY PICK THIS UP ONCE YOU'VE KILLED THE BOSS INSIDE THE LOCKED BARN.

4. Tome: The third Tome is located just outside the barn which you need to unlock. When you've unlocked it and killed the boss inside, head to the ladder that's towards the back. Climb it, turn right at the top and run straight as if you're going back outside. At the window you can leap down and to the right to pick up the Tome. 

5. Tome: The final Tome is incredibly easy to find. After you've leapt from the barn, head through the corn field and stick to the left hand side. Keep heading left until you hit water. At the end of the path (surrounded by soil on both sides) is the Tome sat in a box.