Knowing that the strength of the branches under his hand was limited, the Undead Overlord understood that if he simply left them to fend for themselves, they would likely perish soon. The bond between the Undead Overlord and its branches was inevitably far more intimate than that between other cult lords and their vassal tribes. In this regard, even if the Undead Overlord couldn't protect them due to the agreement between the cult lords, it could use alternative methods to safeguard the branches under its command.
Officially, the Undead Overlord had once exiled a batch of his undead monsters, asking them to station in each branch. Usually, the exiled undead monsters stayed uninvolved in the affairs of the undead branches, but when the branches faced the threat of extinction, the exiled undead monsters would then step in to crush the invading enemies.