I know you can't skip the mechanics in Skittering Tunnels, so for some it might be tedious to do the dungeon. If you really wanted First Step though, it is like one of the easiest outfits to get in this game. Anyone who finishes the storyline can solo this dungeon, and most people get it within 2 runs. It is a common reward from the box from the dynamic quest.
So again I fail to see why this is even in the boxes, because as they said: "This chest gives costume collectors who missed out on some previous outfits another chance to get them"
You literally can not have missed out o