-Feature: Third and final Siege stage added to Arena, and along with it, the N51 faction make their presence known. They're sturdier than the Nexus Core, but more conservative in their attacks.
-Tweak: The health of Turrets is unaffected by Madness difficulty. In addition, the size of a unit reduces the effect Madness difficulty has on their health.
Update [1.36.a] Patch Notes!
Source: Steam Community (opens in a new tab)