"You know you had to dig deep coming here and I think she made well and truly enough money," Yulong general manager Vin Cox said.
"Congratulations to Te Akau Racing and David (Ellis) and Karyn (Fenton-Ellis).
"She's in the top half-dozen, certainly top 10 mares of all time, she'd have to be. The Zenyattas, the Sunlines, and things like that come to mind but she punches with up there with them."
Imperatriz claimed the Australasian record from Milanova, who has owned it since being sold for $5 million by Inglis in 2008.
The previous record at a Magic Millions sale was $4.2 million, set by Sunlight in 2020.
Imperatriz's sale is part of a historic year in Australian bloodstock after the record price for a yearling was shattered earlier in the year, when Debbie Kepitis and family paid $10m for the first foal of her legendary racemare Winx.
Bidding on the daughter of I Am Invincible, who is in New Zealand and was offered in absentia, opened at $4 million after which auctioneer Steve Davis took bids of $250,000 until $6.5m, before Yulong – bidding under the name Zhijun Zhao – won the day with a $100,000 final bid.
It ends Imperatriz's time with Te Akau Racing, which paid $360,000 for her at the Magic Millions Gold Coast Yearling Sale in 2020, and Te Akau principal David Ellis was delighted with the result.
"She's in the paddock at the farm at the moment, it's dark right now at Te Akau, (but) the young lady who looks after her is in the paddock and she had an iPad and was showing Imperatriz being sold," Ellis said.
"We've got a photo of it so it is quite priceless, really. To break the record for the top price for a mare is really exciting."