Miss Maripony (Real name Twilight Sparkle) - Female - Unicorn
Mane: Dark navy, with a streak of electric blue.
Maripony is a character represented in the background throughout Project Horizons. Strongly connected with both Hoofington (The Hoof), as well as the Ministry of Arcane Sciences. As noted early on, in a memory sphere, Maripony was the lover of Big Macintosh, though they were never married as Big Mac died in the assassination attempt prior to leaving the service and proposing. Maripony was in fact pregnant at the time, as revealed in a memory orb.
As of Chapter 33: Maripony is Twilight Sparkle.
During her date with Macintosh, he is accosted by sailors who are jealous of Maripony's company. Intending to steal Maripony away, they ended up being beaten themselves after one sailor cuts Maripony while she tried to protect Macintosh. The cut caused Twilight's illusion spell to fail; along with the loss of her dress, her identity was confirmed, as at the time of the creation of the memory, convincingly concealing or changing cutiemarks was not possible. The revelation forced Macintosh to break up with Maripony (Twilight) as she was a Ministry Mare and it would not be appropriate for her to be seen with him as he was a lowly footsoldier and it would create a huge scandal.
Note: During this orb it is revealed that Macintosh and Twilight (as Maripony) had sex several times, with Twilight admitting that she used a Zebra Sex book for ideas on positions.
Speculation: One of the possible mothers of Tarot is Twilight Sparkle, who, after losing Macintosh, gave up her unborn foal to a surrogate mother (almost certainly believing she was aborting it, based on dialogue). In turn, this explains Blackjack's ability to open the sealed cases in which Folly's bullets are kept. Another distinct possiblity of proof of Blackjack's ancestry is the study which Lifebloom sends Blackjack into, asking her to retrieve a book for him. It had similar jewel insets as the sealed door used in the test for the Twilight Society; this time, Blackjack is able to open the door, and retrieves a magic book intended to be sent to Marigold to assist in developing Tarot's magic.