Ubisoft and Massive Entertainment have released a trailer showcasing the new faction, named Black Tusk, which will be present in The Division 2's endgame. The best description is that they leave the impression that LMB and Hunters fused.
Black Tusk faction was originally teased at the end of The Division 2 story trailer, where they had simple orders - terminate any Division agents with extreme prejudice. Parts of the faction were already teased though, as the "robot dogs" were shown in gameplay earlier. According to the new endgame trailer, these robotic dogs will be just one of the many tools at Black Tusks' disposal.
According to Massive Entertainment, Black Tusks are the hardest enemy faction they have ever created, insinuating that a lot of thought went into their AI. The developers already confirmed that The Division 2's factions will have different AI, but this was also the case in the original The Division.
For example, it was easy to differentiate the behaviour of Looters who were scattered and unorganised, over Cleaners who introduced lower level tactics with shotgun rushers and long-range snipers and then there was LMB. These soldiers behaved in a tactical manner and always tried to outflank the players, while keeping only snipers and grenadiers in the back line.
Judging from the trailer above, Black Tusks will have similar behaviour, if not improved and / or merged with Hunters' design. They will also exhibit some habits shown by First Wave agents and Hunters, such as extensive gadget usage, with the previously mentioned robot dogs seemingly being the faction exclusive.
What sets the Black Tusks apart is that the will appear on more occasions than Hunters, and they will come in numbers. The only time we saw grouped Hunters regularly in The Division was in The Underground, while Black Tusks are set to invade several player activities in The Division 2.
Unfortunately, the trailer didn't offer any info on Black Tusks' lore, so there is no knowing if they are in any way connected to the First Wave, Aaron Keener or the Hunters.