Inspired by Waking Nightmares AU by KnightMysterio.https://www.fanfiction.net/s/7360739/1/Waking-Nightmares

Some of the mercenaries from Mann Co start finding themselves in a world dominated by colorful ponies. must admit it is a nice place, the ponies are a very welcome species but slowly the mercenaries start to realize there is a reason why they were brought here and why all of them are somehow connected to the element bearers.
an ancient darkness is gaining strength and if they and their new pony friends cannot stop it, then both their worlds are in grave danger.