2006-09-25 : Like any creature, if Mistform Ultimus becomes another type as the result of a spell or ability, it will lose all its other creature types.

2006-09-25 : Mistform Ultimus has all creature types even if an effect removes its ability. Type-changing static abilities will apply in layer 4 before effects such as Sudden Spoiling’s remove them in layer 6.

2006-09-25 : The type “Illusion” is printed on the card’s type line purely for flavor. The Ultimus has every other creature type as well.