I am curious about this Wizard realm spell 'Demagogue'.

Rule book says that demagogue can be used to adjust loyalty of the province.
But it seems that this spell has some more power.
The first mention about it appears on rule book P. 82

But in special cases(such as the demagogue spell), PCs
might be allowed saves to learn whether their characters
fall victim to the effects.

And "Family matters" adventure mentions that

The mage casts a demagogue realm spell on the enemy and forces
him to declare war on the PC kingdom.
The Enigmatic wizard casts the demagogue spell on the PC
regent, forcing him to declare war on his enemy.

So it seems that demagogue spell has some more powerful effect on
the individual PC(s), but I cann't find any other reference what
exactly this spell do.

Any idea or suggestion?