Marvel's deadly symbiotes are always a deadly batch to tangle with. With the start of the Extreme Carnage event, several of Venom's offspring will be returning, including Phage, Riot, Lasher, Scream, and Agony. These symbiotes were created by the Life Foundation and while they don't have as bulky a catalog of comics as Venom or Carnage, they should not be underestimated.
Agony is born from Venom in 1993's Venom: Lethal Protector miniseries. Eddie Brock - the host of Venom - is separated from his symbiote other by the Life Foundation in order to create a group of symbiotes. These symbiotes are bonded to volunteers of the organization as a means of developing a tougher security team. Agony is purple or pink in coloration and has some special abilities that the other Life Foundation symbiotes do not, including acidic saliva used as a projectile and the ability to absorb and reproduce chemicals orally.
First Host
Agony's first host - Leslie Gesneria - is present when the Life Foundation symbiotes free Eddie from imprisonment after his complete separation from his symbiote. They seek him out to learn to use their new symbiote partners and abilities for good following the demise of the Life Foundation. Leslie meets her death in Venom: Separation Anxiety #3 when Scream begins killing off each Life Foundation symbiote one by one. Agony is then imprisoned, but makes more appearances later.
In Venom: Along Came a Spider (1996), Agony became part of Hybrid, a conglomeration of the five Life Foundation symbiotes. They are bonded to Scott Washington, who would use them to regain his mobility following an accident that left him paralyzed. Scott, as Hybrid, seeks out the gang members responsible for his injury and the death of his younger brother. The five are bonded to him until a final separation when Scott is killed by Eddie in an issue of Venom. Up until just after this point, Agony did not officially have a name. The name would come in Carnage, U.S.A. (2011).
The Named Era
Agony returns in Carnage, U.S.A. as a bio-weapon - with Agony as her official name - alongside four of her siblings, as Scream is not present in this series. She is partially bonded to Lieutenant James Murphy of the Mercury Team. She assists in the operation of a rail gun by assisting distribution of the weight and force of the weapon. At the conclusion, Agony and the other four Life Foundation symbiotes are sealed back into cases, up until they meet up with Deadpool in Deadpool vs. Carnage. This series ends in another hybridization, with a partial bonding of the four symbiotes to the Merc with a Mouth.
After Deadpool dismisses Mercury Team's dog who is bonded to each of the symbiotes, it ends up at the home of a broken family. This is their ride directly to Knull - god of symbiotes. They make a brief appearance in Venom #17 and #18, chasing after Eddie Brock's son, Dylan, and Normie Osborn who briefly bonded with Carnage before these issues. Agony is captured, but Dylan Brock frees her and the rest of the Life Foundation as a distraction. King in Black: Planet of the Symbiotes #1 brings all five symbiotes back together as Agony and the others seek Dylan Brock, while Scream - now bonded to Andi Benton - opposes them. Scream incinerates her four siblings, though they manage to escape.
The Future
Agony will next appear in July's Marvel event, Extreme Carnage. The Life Foundation symbiotes are making a bigger comeback. After the events in King in Black, a new era has begun. The event has kicked off with Extreme Carnage: Alpha #1. Agony and her siblings will likely be present all throughout the event.