Text (TS+errata): 3/3. ; ~this~ is every creature type (even if this card isn't on the battlefield). [Oracle 2009/07/08]
The creature type Illusion is printed on the card just for flavor. It has every creature type. [Legions FAQ 2003/01/23]
If this card is changed to a specific creature type by a spell or ability, then that effect replaces all the creature types with the one determined by the spell or ability. [Legions FAQ 2003/01/23]
The "this is every creature type" text is characteristic setting text, so it is not turned off by Humble or Humility. [DeLaney 2003/02/03]