The universe has multiple parallel layers.
The Wizard civilization had acknowledged and proven this point long ago.
"Alien" is a concept and phenomenon that comes from this, both internally and externally.
Internally refers to within the universe where the Wizard civilization resides, and externally refers to the parallel universes of the Wizard civilization, or collectively as other universes.
Clearly, both Link and Elise Clark are "Aliens" whose True Spirits come from other universes.
As far as the Wizard civilization is concerned, externally.
One thing is certain, the True Spirit of Link, the "Alien," does not come from the universe where the Immortal God civilization exists.
Similarly, he is not the special "Alien" predicted by The Saint of Nostrodam before his silent extinction; Elise Clark is.
Indeed, Elise Clark had initiated, accepted, and passed the trials borne by the Special Ruin World.