It's hard to tell what a new season is going to look like based off of the season premiere. Most of the time they use the first episode to clean up any cliffhangers and set the show back to status quo. This was always prevalent on X-Files where the season finales showed us hard evidence and Dana Scully was amazed only to have the genie put back in the bottle with the next season premiere and Scully return to being skeptical. But with the second episodes now in, we can look at what may be in store this season of the Arrowverse.
Now, DC's Legends of Tomorrow is slightly different than the other Arrowverse shows in that it only has seventeen episodes to tell their story, six less than Flash or Arrow. This means they can't have as many disconnected episodes. They started teasing the big bad for the season, Mallus, in the very first episode when Rip Hunter tells Agent Sharpe that the Legends may be what's needed to defeat Mallus. And then in the second episode we see a follower of Mallus summon Kuasa from the water. It's unclear exactly what had happened Kuasa between her getting the Water Anansi Totem in the second season of the Vixen animated series and her return on Legends.
Amaya explains that she is having issues with her Anansi Totem, that the animal instincts are taking over and she ended up hunting down and killing a group of soldiers while she was protecting her village. What this likely means is that magic itself is being affected by whatever the big bad is doing. Perhaps Kuasa get lost in her water powers the same way Amaya got lost in her animal powers and the hooded figure had to guide her back. It also explains why we'll see characters like John Constantine and Damien Darhk, two very magically centered characters in the Arrowverse.
Which means that the key to this season is going to be the identity of the big bad. The name Mallus doesn't necessarily tie into any existing character in the DC Comic universe, but that doesn't mean it's not an alias for a character of immense magical power. And with so many DC villains that would fit the bill, I can't see the show not using an existing one.
We know that Damien Darhk is going to be the driving force for the villains this season, but the impression from interviews with the producers is that he's working with/for someone and for Darhk to work for someone, it would either have to be someone who is extremely powerful or they have something he wants. Now this is a Darhk post Arrow season 4 so he knows he killed Laurel Lance and he knows magic. Which makes him more powerful than the version we saw in last year's Legends.
The key here is the obvious one, who is Mallus. I've seen some interesting on-line speculation that he's Mordru, the enemy of the Justice Society, which would be an interesting choice. I've also seen someone say that Amaya is actually Mallus and another who says it's Damien Darhk. I can't see them using Darhk as the big bad without just saying he's the big bad. Amaya would be an interesting twist, but I can't see them doing that either. I think we need a few more clues before we can make a real educated guess.