What exactly is Territory? For one to be declared by a Fourth Stage and able to block even Givale's mastery over space, it had to have more properties over buffing.
Territory was exactly as the name stated. There were certain methods to calling your Territory, but no surefire way to unlock it. Similarly to a War Sight not everyone was capable of staking claim via Territory.
The most commonly known method is through Synced Nexus. Once the synchronization between two reached a certain level their ideals would blend and form a Territory to suit it. This was the easiest method of unlocking Territory but came at two significant costs.
First, the Territory calling was exclusive to the Synced Nexus. Meaning if the two failed to reach the synchronization level the Territory would not be called. A far cry from the Undead King's willing summon.
The last cost was due to the blending of ideals. The Territory summoned could not be willingly modified. There exists examples of Territory evolving, but its changes could not be directed. This meant that the Territory called via Synced Nexus was almost random. In this it held a similar restriction to that of War Sights.
This was one method for Territory. The usage of the Undead King was something akin to a separate world. By manifesting his ideal to an extreme degree he was able to form it as a Territory. A process not widely known.
A Territory formed by a single individual's ideal was held under a different set of restrictions than one from Synced Nexus. They are as such:
One: All Territory's regardless of origin will not negatively impact outsiders within it.
This is why Stars stated that Territory's served purely as a buff. The infliction of negative effects was limited to Domains. A single person could not wield both a Domain and a Territory simultaneously.
Two: A Territory must be pitched to the World.
This process was a bit muddled. Similarly to that of ascending Stages, the World would judge the Territory and deem it fit. Once called the World would essentially "lend" its authority over a set amount of space to the caller of the Territory. This Authority was what allowed the caller to adjust various properties.
Three: The border of the Territory must be obvious to all witnessing it.
This rule had one loophole. This only applied to when the Territory is called. If someone was already within the range of your Territory, you could call it and entrap them within without stating its border first. Once the Territory had fully manifested, it would become clear where its border lie.
Four: Anyone within the Territory must be free to leave at any given opportunity.
This fell under the category of the first restriction. Preventing those within from leaving would count as a negative effect, and thus would disqualify as a Territory.
Five: The effects of the Territory must be made clear upon calling.
This would mean that under no circumstance would those within the Territory be unaware of what the Territory did. Restricted by this final rule came with the benefit of altering the buff. As long as the World approved the changes, a Territory could change in property the second time you faced it.
These rules may seem restrictive, but the benefits of a Territory made the exchange more than worthwhile. There were smaller restrictions regarding the more particular aspects of a Territory, but those may be reviewed at a later date.
For now, the Undead King's Territory was modified under these new rules: No one may enter without his permission, the undead under his authority would rise again, and in exchange for the lackluster applications he extended the range of his Territory massively.
All of these met the rules and was approved by the World. Those within the Territory were made clear of the undeads rising again. Those outside would immediately find they were unable to enter. And the range was made obvious by the sickly green hue.
To counter a Territory one would need either their own Territory, or a Domain to even out the applied effects. These two options were not available to Akiol, for these power systems were things he wasn't familiar with enough.
Synced Nexus was also something borderline impossible due to how many beings he was Linked with. Summoning a Territory via Synced Nexus was not an option either.
Givale made it clear that they could possibly breach the rule regarding no entry if they attacked the barrier from both sides. However this would be difficult as it meant leaving the current battle. Excluding the helplessness Raven Thread would experience, Akiol doubted the two Third Stages would let him go so easily.
Thus Akiol came to a simple conclusion. Either Opportunity escapes the area she was kidnapped to and helps create the breach, or Akiol finds an chance to escape.
Well, escape or defeat the enemies present.
Souls leapt forward while crying sorrowfully. Akiol swung and cleaved through them all, causing them to be absorbed. Upon reaching Third Stage Star's ability to absorb magic attacks became a passive. This came at the cost that the attack could not be made of physical matter. So ice, water, or earth magic wouldn't be nullified, but light or fire magic would.
The dulluhan screeched and Akiol found his gaze being forcefully dragged towards it. A taunting ability he wasn't able to resist. Several souls flew across the field towards him, their presence only known by their wails and the shift in mana.
Akiol found himself unable to swing his sword towards them. It was very likely the taunt ability restricted his movement to a certain degree under a specific set of conditions. Rapidly adjusting the direction of his swing he managed to cleave through one of the souls but was forced to receive another.
The moment he received the damage from the soul his gaze was no longer locked dropping to the ground rapidly he sheathed Stars and dashed forward.
As he had an intuition of, the taunting ability of the dulluhan restricted Akiol to making any movements except when they involve the dulluhan itself. This was his eyesight, movement, and attacks. Managing to circumvent this restriction by making a pointless attack towards the dulluhan, the trajectory of the swing just happened to have cleaved through the incoming soul projectile.
This of course was intentional, but far too late. As his foot dug into the ground he noticed a strange weight on his shoulders. A similar pressure to that of Dot's War Sight. It tugged at his movements to slow him, but not at the point of being too detrimental.
{Way of the Galaxy: . . .}
Dashing through the horde of undead he blasted them to the side. Approaching the dulluhan he unsheathed his blade as he performed a spectacular slash as he passed by. Resheathing his weapon caused a massive swirl and explosion of Aura, destroying the undead in its vicinity.
{Supernova}!