Frozen world

Sasha himself does not know how it turned out that he with his own hands destroyed a prison in which the ancient Elb had been imprisoned for many centuries. But when the choice is in front of you to help a person who is in trouble, or to quit him alone with his problems, you don’t really think, you just do what they ask. A few hundred years ago, Rogrik, a strong Elb, was already trying to break through the border between the worlds so that the swamp would pour into our world. Then the firsts managed to sharpen him in the subway, and now the dungeon of Rogrik is destroyed. And he is able to pave the move and let the swamp into our world. Is it possible to stop someone so powerful and so embittered?
For senior school age