Avengers: Infinity War Trailer - 8 Most Revealing Shots
4. Black Panther Fights An Outrider
The trailer features an alien race that we've never seen in the MCU before, creatures that can be seen battling on what we assume are Wakandan plains.
These creatures look like Outriders, genetically-modified beings that are created to serve a specific master. Once they've done their job and their master is satisfied, they are allowed to die.
It looks like the Outriders will serve as Infinity War's cannon-fodder villains, giving the Avengers plenty of targets to punch, kick, shoot and destroy. However, that's not the only purpose they're likely to serve.
In the comic-book storyline 'Infinity' (which Infinity War seems to be taking heavy cues from) a lone Outrider arrives on Earth. This Outrider discovers that most of the Avengers aren't on the planet, leaving Earth largely undefended. The Outrider tells this to Thanos, and The Mad Titan uses this information to his advantage, deciding to invade Earth.
Infinity War could use elements of this storyline. Thanos could send an Outrider/army of Outriders to scout ahead for Infinity Stones (maybe the Soul Stone is in Wakanda, and that's why a huge battle takes place there) while he deals with some of the Avengers.
Or, the Outriders could just be there so our heroes have something to fight. Either way, they look very menacing and are superbly designed, but whether they'll be of any use to the plot remains to be seen.