Rift had a mechanic much like Fates here in which you have minor, mid-tier, and large scale.
What happens is an area will have a Rift open and you and your group would work together to put it down. Some were soloable and others required help or be geared.
Then you got the large scale that is zone wide in which everyone in the zone spreads out to take on multiple threats at the same time. It usually ends with a world boss popping up and all units converge to take out the singular threat.
Edit: forgot to mention one can start small and just explode into an extreme version of a non-invasion level Rift if just many people are active in it. They also aren't level dependent so you can do one in the baby starting area as a max level and it still be a challenge cause everything is attuned to the individual.