Originally built as retreats from the strict etiquette of court life at the château, the Trianons, while dwarfed by the sheer size of Versailles, are magnificent 'mini' châteaux in themselves, far removed from the actual palace that they could be considered separate estates independent of the palace.
Whilst the Hallowed Nocturne is active all throughout the palace's grounds, the Grand Trianon acts as their designated meeting and housing location after nightfall.
The Rosen Epiphany is quite aware of this location but there is an unspoken, unwritten agreement here that neither side may invade the others' main locale.
