What happens when you combine TF2 and HL2 here what we got!
Technically there is more than 1 version:
Lambda Fortress (Team Fortress: Co-oP)
Lambda Fortress: Extended ( Team Fortress Co-oP: Extended)
Lambda Fortress Extended: Community Edition
we gonna focus on Extended version
Overview
Lambda Fortress is a crossover mod in which players can play solo or cooperatively as the mercenaries of Team Fortress 2 through Half-Life 2 and various other supported Source campaigns. It is a rebuild of the previous iteration of the mod, Lambda Fortress: Extended. This version was created after said previous iteration became too buggy and bloated for the previous team to continue developing for. Currently, the new version of the mod is in closed beta being worked on by CoaXioN, aiming for a stable and bug-free experience.
Story
As the rift in time-space persists, portal storms have become more frequent and numerous with one of them opening a gateway allowing a team of mercenaries to arrive in the streets of City 17. Dazed and confused, the mercenaries struggle to adapt to the oppressive ambiance of the Combine regime as they attempt to find a way home and fit in through any means necessary with no qualms of resorting to their preferred and favorite way, violence.
Trivia
Technically, the current version of the mod is the third iteration of Lambda Fortress, coming after the original Lambda Fortress by Nicknine and Lambda Fortress: Extended.
Another popular mod, Fortress Connected, is built off of a fork of Lambda Fortress: Extended, some fixes from it are also used in the new Lambda Fortress.
you can download at:
https://drive.google.com/file/d/1_pk_8gvy1Y8jKfm9YISJ2CvICLo6O07f/view