Synopsis
On the island of Rugen, Germany archaeologists have unearthed a box but now someone has killed them with her sword. The box contains the helmet of Erida, Goddess Of Hate, and the woman describes herself as her last priestess. But we know her as Sin, daughter of the Red Skull.
In Avengers Mansion Edwin Jarvis has alerted Captain America (Steve Rogers) to a crisis. Cap's there to inaugurate a new Avengers team that he thinks is needed in a world where mutantkind is recovering from the Fall Of X event and Dr Doom is the new Sorcerer Supreme and there's loads of new vampires who can now survive in daylight (both since the Blood Hunt event). During Blood Hunt he led an impromptu team of Avengers to protect New York from the vamps (in #14-16 of the current Av series). And now he's instituting the Avengers Emergency Response Squad (AvengERS) to handle such crises.
Coincidentally the 1st 3 invited members of the team arrive:- Photon (Monica Rambeau), Shang-Chi and Wasp (Janet Van Dyne). Steve welcomes the 2 female frequent flyers (and sometime leaders of the Avengers) plus Shang (who was part of the 2010 Secret Avengers, the 2012 Avengers and the 2014 Avengers World series) and tells them that more chars are on their way but they've got an immediate mission to attend to. We learn that Sin is using the ancient psionic artefact to start an infestation of hatred. Shang uses his magic Ten Rings to whisk them to their destination of Rugen.
They arrive to find literally red-eyed people fighting each other and causing mayhem. Having 3 ex-leaders of the Avengers starts to cause its own chaos as Photon pre-empts control from Cap. Meanwhile just across on the mainland in Stralsund 4 members of the Serpent Society (Black Mamba, Puff Adder, ex-leader Sidewinder and newbie Tiger Snake) are using the cover of the nearby conflict to sneak in to steal a large old wooden cask. And Sin continues to rant that hate is the oldest emotion and as Erida she feeds off it. And continues to expand the range of her influence. It even inflames the 3-way leadership rivalry. But Shang-Chi uses his martial arts training to keep control and strikes the other 3 in a specific brain area to temporarily numb the hate circuit (insula and putamen). They agree this gives him the right to declare "Avengers assemble".
Back in Manhattan Hawkeye (Clint Barton) has arrived at the Mansion and is sitting at the round meeting table. He decides to await the next crisis but meanwhile gets out a pack of cards. Lightning (Miguel Santos) is next, complaining that they haven't been in contact since the Avengers: No Surrender epic. Then She-Hulk (Jennifer Walters) and then, surprising them all, college student Lightspeed (Julie Power) of Power Pack (who obliquely refers to her romance in Avengers Academy with Majesdanian alien Karolina Dean of the Runaways).
Sin attacks Cap's shield claiming to have broken it once before (I think she means Fear Itself #5 but it was actually Odin's brother the Serpent that did it). Wasp attacks her but is repulsed. Shang-Chi is next and then she grapples with Photon. But Cap and Shang launch a shattering counter-attack with shield and fists. But the bloodied villain calls on her hate-filled horde to attack the heroes. The Avengers don't want to hurt the possessed people but Photon launches herself out of the melee to attack Sin directly. And Wasp has a plan.
Hercules has joined the gathering at the Mansion. They haven't started playing cards and Jen says it wouldn't be a fair contest because Miguel outplayed the Grandmaster (bluffing him at poker in Av#689 at the end of Av:NS). Hercules says he's beaten an Elder Of The Universe too, but Jen objects that outboxing Champion isn't the same. (I can't remember such a fight. Marvel Fandom Wiki suggests it was in She-Hulk (2004) #7 but I find no mention of Herc there, and if he was there he'd have to be 1 of the losers). Wonder Man (Simon Williams) then completes the assembly and mentions that Herc is 3-up in their arm-wrestling contests. Julie wants to drop out when she thinks they're playing for money which she can't afford but Simon assures her that the loser just has to wash the dishes. She tells Wondy she's seen 1 of his movies, but only because her dad's a fan.
Sin is feeding off photon's anger but Monica tells her she's taking in loads of electrons too. The villain dismisses science as ineffectual against magic. Then Wasp flies up her nose and causes an electric spasm in her head. Photon suggests they focus on destroying the magic helm. She borrows Cap's shield as Sin sneezes Wasp out. Cap and Shang start battering the helmet as Photon flies up to space. And then she zooms down to slam the shield in Sin's face. The foe boasts that they've only delivered her into the arms of Erida. And she burns to ash. And the German populace recover from possession.
At the poker table Simon calls but Jen says she can tell he's bluffing. Her courtroom experience and all his big screen appearances mean that she knows his tells. Simon tries to laugh *that* off as a bluff but yet he folds. Herc reminds him this is just a friendly game, but also 'reminds' him that his Olympian Allspeak power means that he can read everyone's body language too. Then the others' reaction shows that they didn't know about that. Jarvis starts to bring in food but a final late arrival joins them - Night Thrasher (Dwayne Taylor). Lightspeed finally lets out her inner fangirl and NT opens a box to reveal matching team jackets for them all, and some other stuff.
A final epilogue in the Serpent Stronghold caverns below Rawling, New York shows us the large gathering of the Serpent Society with their leader Viper now calling himself Pit Viper (but fully-masked so it might not be him). And it seems that Tiger Snake is someone he personally brought into the team. He tells Puff Adder to pour some of the aged whale oil, steeped in suffering and waste, from the cask into a glass bowl where it presumably mixes with other ingredients which the boss says will produce the Serpent's Tears. He claims they will be a deadly and marketable weapon, but will also honour their backer Mephisto who will weep the Tears. And we see his image in smoke from the bowl (unless he's really there).