Black Garius

Black Garius is an NPC in the official campaign and probably the most antagonistic NPC in the entire game, despite him having very little face to face contact with the PC.

Description
This old wizard has a deep, intimidating stare and the smile of someone who is rarely denied the things he wants. He is dressed in the regal, almost pompous black robes of a Hosttower mage.

As a Hosttower Mage
He is the driving force for the start of the games events. He has been working with the Shadow Priests who want to raise up the King of Shadows and wishes to use their power to increase his own. He works out of a temporary stronghold in the Crossroad Keep within Neverwinters boarders.

His cohorts, commonly seen with him in cutscenes, are Torio and Lorne.

The rough events he works on before the PC kills him follow roughly as so:


 * He works his way up the Hosttower and into a position of some power.
 * He steals the codex of golems from the Arcane Brotherhood and blames it, or makes it seem as if the nearby islands have stolen it, leading Luskan to put the majority of its forces to the location. This leads to:
 * Him having control over Torio, the Luskan ambassador to Neverwinter
 * He being able to take forces of Luskan's army and arcane brotherhood for his own ends
 * He was able to escape the notice of the Arcane Brotherhood since it is noted by Sydney later that Garius' plot was not part known to Luskan.
 * He provides resources for the Shadow Priests operating in various locations such as near Fort Locke, and Old Owl Well, allowing them to raise up undead cohorts to try and kill the nearby Neverwinter forces. The Orcs in Old Owl well were meant to provide a distraction to the Greycloak army.
 * Presumably, he researches the rituals of the shadow weave and the Reavers.

The PC then comes into the game and will upset plans at Fort Locke, killing the Shadow Priest and his minions there.

Then the PC eventually makes it to Old Owl Well and destroys the Shadow Priest presence there, and upsetting the Orc population so a civil war breaks out.

After this, Torio, Lorne and Garius presumably plan to kill the residents of Ember themselves. Lorne is sent, disguised with a potion from a nearby Dryad in her glade to look like the PC, with several assassins from Luskan, to kill everyone. Using Torio he forces the PC to be captured and tried in Luskan - although this fails and the court proceedings take place in Neverwinter.

After this, it is revealed where Garius is - at the Crossroad Keep, leading the PC to defeat his small Luskan force comprised of elite warriors and Arcane Brotherhood members. He himself doesn't fight, being part of a ritual - to become a shadow Reaver - which he presumably started once the champion contest between Lorne and the PC was decided.

As a Reaver
He becomes a Reaver after the burning bodies of the Arcane Brotherhood mages and himself are burnt near Crossroad Keep. Obviously some part of the ritual worked. They seem to wander off, presumably to the Illefarn location located south of Neverwinter.

In his new form he pretty much doesn't do anythign until the King of Shadow's army is lead to attack Crossroad Keep. He personally assaults the inner keep, and after having his true name read out flees.

The final encounter is with him in the final Illefarn chamber where the King of Shadows is. He tries to persuade people to betray the PC (at least one always will - either Sand or Qara). The PC then can kill him as normal, leading to the final fight with the King of Shadows.

Motives
Supposedly, he was going after some of the raw power that the Shadow Priests could provide, using shadow magic and, more importantly the shadow weave. Once he is a Reaver however, he is not at all caring about his own power and works only for the King of Shadows.

He also has very little background, and unlike Lorne has no relation to anything the PC knows about at any part during the initial parts of the game. It is unknown how he works with the Shadow Priests, how he has a hold on Torio and why Lorne follows him, and where he came from before the Arcane Brotherhood, and how he found out about the King of Shadows power.

Since there seemed to be no official leader of the Shadow Priests, therefore it seems as if Garius made the organisation (if there was anything to be made of it before he started on it) powerful by himself using Luskan's resources.

As an antagonist
Special note must be given that, even though he is supposedly the most prominent antagonist NPC in the entire campaign, the PC meets him face to face a total of 3 times with no real extended dialogue for the first two.

He also dies without using his own mortal powers in the first Crossroad Keep encounter, only fighting as a Reaver after this.

The other times the PC sees him are in various open cutscenes, and a few minor times - such as when his image is projected to a Shadow Priest near Fort Locke.

He also lacks any real deed which affects the PC personally. West Harbour is not attacked from him, but instead is the Githyanki. He also doesn't have any hand in the proceedings in Neverwinter beyond controlling Torio, the works of the thieves guild isn't anything to do with his plans.

Funnily enough, he has little antagonistic motives beyond working for the King of Shadows later in the game.