The Knight is an Ascendancy Class for the Duelist Class, a DEX / STR hybrid class that starts on the bottom of the Passive Tree, similar to the Mercenary.
At Exilecon, GGG provided some details about the Knight and possible Ascendancy points.
While the Duelist specializes in Swords and Stances to swap between different bonus effects, the Knight specializes in:
Buffing/Summoning Allies
Spend Glory for unique effects
Banners
Knight Tree
Knight Passives
Summon Squire
The Knight is able to bring a Squire in to combat. This Squire can be equipped with equipment and skills to coordinate in battle.
This can lead to interesting builds as you can use the Squire to apply certain effects or debuffs to empower your main Knight character or vice versa.
Honourbound
Grants Skill: Honourbound Blade
Gain 5 Valour every 2 seconds while a Rare or Unique Monster is in your Presence Gain 5 Valour per 10 Glory consumed
This passive allows you to generate Valour passively and through Glory, which sends out waves of justice to damage enemies.
Bannerlord
The Bannerlord passive grants unique banner effects that can be used to empower your character and your Squire (if you choose to allocate it).
For example, Vaal Warbanner causes the area to become drenched in blood, adding additional damage to attacks in range.
Glorious Entrance
Glorious Entrance adds the Liberator's Chariot Skill, allowing The Knight to mount a ghostly steed-led Chariot that crash into enemies after building up enough Glory
More Knight Ascendancy Passives Reveal Coming Soon