Idiot
Sam is currently in the forest sitting on a tree branch as he chewed on sugarcane.
Raiju, Dia, and the forest bear which Sam decided to call Barn. As it was already established that his naming sense was not good and taking advantage of the fact that the bear has no naming sense either, he just gave that name to it.
There is a stream nearby.
This stream flows through the city and the only entry point that is completely restricted with formations and barricades.
But Sam is not using this for entering this place. He is more inclined to use it for something else, so he created a small mounting frame in the middle of the stream, and placed a metallic barrel. The barrel is none other than the undying liquid waste he got from the Banished realm.
He didn't let it go all at once, as the stream is constantly flowing, he has to constantly replenish the inclusion of the waste.