Thats a good question. I should probably clarify that. I would assume that it would be very hard to acquire. I did some research and this is what I have found:
"Five of a Kind When playing with wild cards, five of a kind becomes the highest type of hand, beating a royal flush. Between fives of a kind, the higher beats the lower, five aces being highest of all."
While there is no wild, I think the rarity should be similar with a multideck draw.