If you have 2 friends this will be easy to achive, since the can pick up and carry a Tome to the end.
If your trying this solo, it helps alot using Sienna (Fire mage) and as soon as you whant the bots to replace there Medic kit/bottle, you need to kill yourself. To do so make sure you use up your power enough to make the fire turn against you and the bots will revive and heal you.
I allways waited for the bots to enter the wagon before closing and finishing the level.
For the locations, I used this video:
The old video have been deleted, try this one instead
The Enemy Below