Wall of Thorns/1.03

Temples
Walls of Thorns are created through the Nature magic spell that shares the same name and requires 8 points of mana to cast. They are much smaller than any other wall segment in the game and are slightly weaker by 100 hit points. Their sole purpose is to be a durable obstruction that can be raised immediately when you have need of them, adding a blockade between the enemy and your ranged units / buildings. Comically, they can be summoned around enemy towers to obstruct their firing path - preventing them from being able to successfully fire off one of their non-electrical ranged projectiles.

Trivia
-Game files indicate that this building costs 50 Crystal and has a build time of 10 despite it not being build-able.