This mod changes the enemy spawn tables to make the late game harder.

In vanilla, the maximum spawnrate for behemoths is 37.5% at 1.0 evolution.

In this mod, Behemoths start appearing at 0.85 evolution instead of the usual 0.90.

By the time evolution reaches 0.95, the medium and big biters stop spawning entirely. At that point, every biter and spitter you see will be a Behemoth.