Since Super Dragon Ball Heroes' promotional anime series adapts an arcade game that exists outside of the main series canon, it's allowed to blend all sorts of franchise players in surprising new ways.
One such addition was Cooler, who's next move may be just as surprising as his alliance with Trunks as the Dragon Ball Heroes anime heads into its next arc.
In the latest episode of the promotional anime series, the pieces were put in place to both end the Prison Planet arc and tease the start of the Universal Conflict: Dawn of War arc. Super Fu continues his assault against Goku Xeno and Vegeta Xeno after the Prison Planet starts breaking down, and says that "they" will revive soon, thus completing his objective.
Satisfied with his work, Fu gets himself out of there by cutting open a portal with his sword, but before it closes, Cooler chases after him, with the portal closing behind him. Fu's main objective seemed to be reviving Zamasu and a few others (as demonstrated by the end of the episode), but although Cooler seemed involved with the Prison Planet experiment, he's definitely an enemy to Fu.
Cooler first appeared in the anime after breaking Trunks out of Prison, and thus acted as a sort of ally to Trunks and the others as they all tried to figure out how to get out of Fu's shenanigans. This was further cemented when the Evil Saiyan Cumber arrived, and Cooler was one of the first to fight against him.
Though Cooler was pushed to the sideline as the episodes continued and focused more on Goku's battle with Cumber, this return to Cooler implies that he'll play a key role in taking down Fu. Cooler's most likely still angry for Fu putting him in the prison along with the others, and now that fans know Fu was building up energy the revive a mysterious group of five powerful warriors, Cooler will undoubtedly hater the fact that he was used. Now it's just a matter of where Cooler followed Fu too, and hopefully that will be revealed as the promotional series rolls on.
If you're unaware of this arcade game the promotional series is based on, Super Dragon Ball Heroes is the latest digital card fighting game and the top earner in the digital card arcade scene in Japan. Developed by Dimps, the update brought enhanced graphics and the ability to play as seven characters at the same time and provides all sorts of fantastic fan-service never seen in the original series.
The new arc is set to begin with Episode 7 of the promotional series, which is set to premiere January 10 in Japan. It's titled, "Zamasu Revived?! The Curtain Rises on the Universal Conflict arc!" and as the title implies, teases the return of big Dragon Ball Super villain, Zamasu, along with other major Super multiverse favorites like Jiren, Kefla, and Hit.