Balanced Godhood

A limit imposed by the nexus. "Authors" may not directly harm "characters" who are not their own and "characters" cannot harm authors who are not their own. It is fine if the author allows their own characters to harm them.
Characters and author incarnates are immortal when on the Nexus plane. Statuses will remain in effect upon returning to their own world. 
Bi-lateral conflict will result in instant teleportation to Nexus Node - "The Arena" 
TL:DR: 1. Authors and characters can't hurt authors/characters respectively that are not theirs. 2. You can't hide in the Nexus forever and simply expect some thing that was about to kill you in your original world to not do so.

Manifestation

An attack against a target you are not allowed to harm is completely neutralized. All effects and force are canceled at the point of impact. The target will not even feel the air displaced from said attack. That being said, if you are not allowed to damage them, then they are also most likely not allowed to damage you either.
Continued attempted attacks against an illegal target will result in the summoning of 1 or more Nexus Wardens and potential removal from the Nexus.

Localization

Immortality and innate respawn mechanics possesed by characters are limited in Nexus Node - "The Arena".

Type

Metaphysical, Supernatural