Rhoy will invade offline players in the Grave of Saints, when the player approaches the ladder leading to the top levels of the area.
It is important to note that Rhoy will not spawn unless the player is offline.
Rhoy wears a full Aurous' Set (Transparent), as well as the Illusory Ring of a Conqueror and Illusory Ring of the Exalted pair. He wields an invisible Shotel +5 and Heavy Crossbow +5. The final result is that Rhoy looks naked, when he is in fact fully equipped.
Rhoy is actually a very average Phantom, and poses no threat in and of himself. The real danger of the battle are the rats that will ambush the player: These will drop from the ceiling behind the player, and attack them from behind unexpectedly.
Rhoy is notable for being very easily farmed. He will spawn up to 15 times per game/Bonfire Ascetic. This can be useful for players trying to max out their Way of Blue or Company of Champions covenants. Rhoy also has a 100% chance of dropping an Awestone if the player is a member of the Company of Champions. Players should start to the Grave Entrance bonfire. From there, it is recommended to stay at the top level until all 5 rats have dropped and been killed, especially after NG. Once done, players should jump down the ladder, and immediately climb it. This will trigger Rhoy's invasion.
After about 15 cycles, Rhoy will stop spawning, and will require a Bonfire Ascetic. The bonfire this should be used is NOT the current Grave Entrance bonfire, but rather the first bonfire of the area: Harval's Resting Place.
In Dark Souls II: Scholar of the First Sin, Rhoy will invade only once in NG, but he will invade infinitely if the Bonfire Intensity is 2 or higher and the player is in the Company of Champions covenant. He also has a chance to drop Awestones as normal drops, effectively rewarding 2 Awestones for a lucky kill.