There are ancient terrors in TFTD mod TwOTS, they appear on map like USOs and roam aimlessly, also they have uniq sprites when you check target visuals, looks cool, so I am sure making something like that lategame here is a good idea, cause you know, having 3 alien infested countries and shooting down 7+ alien crafts each day isnt exactly subtle. Its like aliens launching an Overspawn on Mega Primus in X-Com apocalypse.