Note:I don't own Doom or The MCU
Five years later
After Thanos's demise,the world has pretty much moved on,people gone on with their lives without their former friends and families.All expect The Avengers.
Meanwhile in the Doom Slayer's ship...
After The Mad Titan's death,the Doom Slayer decided to stay in Earth since he is bored as their are no demons,or anything for him to slay,so he turned the ship into a makeshift weapon lab and he equiped a spear in his Super Shotgun,a shoulder launcher that uses Argent energy grenades and he ripped off his two shoulder pieces,exposing his arms.
(see his Doom Eternal look)
Meanwhile at Tony Stark's house
Tony Stark has pretty much abanded his old lifestyle as an Avenger and he married Pepper Potts as his wife and they had a daughter known as Morgan Stark.He overall left his past behind,but,deep down,he was still overwhelmed by grief that he can't bring everyone back.
Meanwhile in a storage in New York...
Scott Lang was still stuck inside the Quamtum Realm inside his friend Luis's van,he was stuck there for five years as Hank and Hope were both victims of the snap and since they were gone,no one can release him since no one except them has any knowledge on the Quartum Realm,But,a rat inside the van accidently messed with the control pad and therefore bought him out of the Quartum Realm after five years.
'What the hell?Guys,where are you,what is this place?'he exclaimed,but he knew the first thing to do after he's out is that to check on his family after five long years,but in the way,he came across a memorial of the people who got snapped away,he is unstandbly confused and he looked in the boards to see if anyone he loved got killed by the snap.
'No,No,No,this can't be happening,this can't!'he tried to found any names that he known,but to his surprise,he can't found any of them,but what he came across,was even more shocking that that.
One of the stones has the name'In memories of-Scott Lang'.
and then he figured it all out,'The Snap caused alot of people to disappear and since he was stuck inside the Realm while it occoured,the people regisded him as dead.And then he rushed to his house to see him family,or what's left of it.
Hello?Cassie?Maggie?Anyone?'he knocked the door of his former house,just then,a teenage girl answered the door,'Dad?'That's when he realized that the five hours he had spent inside the realm,five years had passed in the real world,and that teenager girlthat answered the door was his daughter,Cassie Lang,which is now 17 years old.After they had a touching reuninion,he decided to find the Avengers,or what's left of them.After that,he went to the Facility and in the process,he saw The Doom Slayer's ship and he went to the door.
Meanwhile inside the Facility...
The remaining Avengers were trying to have a plan figured out to bring back everyone without the Infinity Stones as they were destroyed,just then,they recieve a voice mail,and Natasha said'There's a visitor on our door.'and Rhodey said,'Maybe it's just Doomguy borrowing more parts for his weapon modifications,he often does that.'and Steve said,'Really?Doomguy?That how you decided to call him?'Rhodey responded him,'What?I think he likes that.'
Natasha breaks their arguement by saying'Guys,shut up for a while.It's Scott.'
At the door,Scott replied with,'This is Scott Lang. We met afew years ago, at theairport,inGermany. I was... I was the guy who got really big. I had a mask on, you wouldn't recognize me. Ant-Man? Ant-Man, I know you know, I know you know that.Also,are we getting visitors?Because I think a saw a space ship outside.'