Most summoning magic not only causes monsters to appear either near the caster or in a remote province of the caster's choice, but also binds the monsters to ensure their loyalty. These monsters are treated as belonging to the caster's side. If summoned remotely as an attack, the victim will know who did it, since the monsters' loyalty is known.
This is not always the case.
Some summons do not guarantee such control, and instead may cause the monsters to be flagged as Special Monsters instead of belonging to the caster's side. Such monsters are hostile to everybody except other Special Monsters.
If summoned in battle, they will attempt to kill everybody on the battlefield. If both sides summon such monsters, they will unite in their bloodlust.
If summoned remotely, they will be announced as Special Monsters -- and the victim, if any, will not be told who summoned them. They will also not claim the province for the caster if they win -- in such a case, the province will be independent after the battle unless the defenders retreat inside a fortress in the province.