Oh yeah, garbled happens when I have marbles in the mouthes on my fingers.

Sneakers is the temp-name of my player, he doesn't have a real name so instead of calling him by Alias X he put sneakers down. Why it's mindfire is one of the mutations he has on his claws, giving Phage a disease application in itself, thus it's now Mindfire Phage-- and because Sneakers is the source of this Phage it's Sneaker's Mindfire Phage.

Legendary diseases are diseases of legend. Look out!

As for size and creature changes:
Phage becomes a creature if it's size increases, raising it to Diminutive size and changing it to a swarm subtype in addition to any other subtypes the host creature currently has and changing it's type to be animal, abberation, outsider, vermin, construct, ooze, elemental, fey, plant or undead types (whichever is currently closest to the host), this type change does not grant any abilities nor does it grant it an HD or change any of it's stats.
Perhaps it should make the wording more detailed to include that the effect ends if it drops down a size again. It gains a size if the size increase teratomorph is gained, not if enlarge person is cast nor due to his minor shape change that allows size change as it states it works only as enlarge person where as evolutionist is a flat size increase similar to a creature HD improvement.

Activated means it has gained sentience.

I'm re-doing the statblock for this in a bit and adding that it also gains attribute points gained on levelup, as he has upgrade mental stats with those.