Quote Originally Posted by ObsidianFire View Post
Voidsent can't make a portal to the Source without someone on the Source summoning them. They don't just travel to the Source randomly.
While many Voidsent are summoned to the Source, not all of them are.

There's things such as during the SB WHM quests where Voidsent portal themselves in to try and feed of the Padjal's uncontrolled Aether. There's places like Haukke Manor which become infested with Voidsent without anyone actively summoning them (Unlike, say, Tam-Tara hard), you have open world areas such as Northern Thanalan where Voidsent appear and gather seemingly at random.

This suggests that Voidsent CAN come to the Source of their own volition, though, I suspect there's some limitations to it, such as them being unable to CHOOSE to come to specifically the Source and instead just sense high levels of Aether and go to it completely oblivious to what shard it is on. Meanwhile summoning would be more direct travel, allowing specific entities to be brought to specific shards (As seen by the many times people summon big bad demons to fight against us)

As far as the "needing to possess a body" thing goes, I'm a little confused on that. Since, for example, in BLM and RDM quests, there are times when enemies open up portals and giant Chimera's come through. With no evidence of having any bodies around (Certainly not giant Chimera ones). I mean, these instances of summoning suggest that these Voidsent are coming through the portals body and all (Though, I suppose it could be a case of artistic licence where devs didn't feel the need to keep putting various bodies around the place for Voidsent to inhabit)