Captain America is one of the few mortals worthy of picking up Mjolnir, as can Superman and Wonder Woman in certain crossover events. None of them have access to any of its powers and can only use it as a weapon. You need a strong moral code, but also a willingness to kill to access Mjolnir’s full abilities. Thor is one of two that can access the full powers of Mjolnir. The other is Beta Ray Bill. The Ballad of Beta Ray Bill brings this other worthy hero to the Avengers cartoon universe.
Plot on brief: The Korbonite people are sent adrift in the cosmos by Surtur, who uses their star to reforge his weapon. Thor goes to investigate and is attacked by Beta Ray Bill, who shocks Thor by picking up Mjolnir and beating him with it. Beta Ray Bill gets called to Asgard and attacks the other Asgardians. Despite his initial hostility, the Asgardians come to Bill’s aid, up to and including crafting for him Strormbreaker. Thor, Sif and Bill return to Skuttlebutt and fight off Surtur’s forces. After it is dealt with, Sif offers her aid to Beta Ray Bill, which he declines. Sif and Thor return to Asgard, with Sif now having a better understanding of why Thor likes a certain mortal.
This is what an adaptation looks like. The original 4 part story was condensed into a 22 minute episode leaving core elements unaltered and making only necessary changes. The big one is Stormbreaker creation now has more weight to it. Originally, it was a plot device that allowed Thor to continue journeying with his trademark. Now, it is a crucial plot element that will bite the God of Thunder in the ass someday.
The other plot thread running throughout is a nod to the Lady Sif and Beta Ray Bill storyline from the comics. For a time, Sif left Asgard to aid Bill in his quest to find the Korbonites a home. In addition to traveling companions and battle buddies, they were also lovers. Elements from the comic were preserved in the episode, including the attraction each feels for one another. Although Bill does reject Sif’s offer of aid, it is obvious that it pained him to do so. For her part, Sif acted more like someone who was rejected. Who knows maybe in the future, Sif and Bill will travel together, but right now that plot thread will be left unresolved.
The only complaint I have is that it tried to advance the Asgardian storyline too quickly. The Beta Ray Bill stuff needed to be one episode, but the Surtur threads could have been spread out over a few more episodes. It seemed a bit forced to place them all here. I suppose this was necessary because there are other plot lines that need resolution and only 18 more episodes to go.
All in all, a very memorable episode from an vastly improved second season.