NHF – new heroes for Heroes V 3.1.

Could you elaborate on how you plan to guard the portals?

- If there's only one guard: place the same guard on all sides (if it's one-way, always place the guard in front of the entrance, and remove it before the exit);
- If there are multiple guards: choose a guard at the entrance and place it on all sides (for a one-way portal, choose only at the entrance and remove it at the exit).

When destroying the guard at two-way portals, remove all other guards from the other sides of the group.

Added 1 minute ago
Then, only the non-creature units will remain untouched.