So after seeing people say Loki is the mother of Sleipnir, I HAD to do research. I poked around on wikipedia and here’s what I think happened.
So sometime just after the finished construction of Midgard and Valhalla, there was a builder who offered to build them walls and towers to protect the new cities.
In exchange for his services he wanted the goddess Freya.
The gods eventually accepted to give freya for his services, but with conditions. He could not have help from any man, and he had a time limit of 3 seasons.
((a single man building 2 cities worth of national defense in the time limit of 8 months in exchange for a woman… ouch, freya must’ve been something all right to have so much worth))
With some influence from Loki ((sympatized with the builder- who only loki discovered that he was a frost giant)), the builder was allowed to have his horse help- as the horse was impressively stronger than the builder and even some of the gods.
However, the gods did not want to give up Freya. The builder and his horse were like 97% finished with 3 days left, and the gods became frantic the closer the deadline came. They turned on Loki ((for his sympathy and semantics I assume)) and told him to sabotage the builder so that the builder would fail. They said the didn’t care how he would make the builder fail, as long as he failed or else Loki would be tortured and killed.
Loki decided the best scheme was to lure the stallion away from its work.
In the guise of night- Loki took on the form of a mare in heat. ((The builder couldn’t blame anyone for sabotage if his partner abandoned him by choice and had no way to entice his partner back.))
both fortunately and unfortunately for loki, he was successful in getting the stallion to chase him, and they ran the entire night to put as much distance between the builder and the stallion as possible.
the next mornig, the builder was tired from working without the stallion and his true form as an ice giant showed when he collapsed. At that point all oaths taken by the gods were broken and Thor was sent out and killed the builder. ((cause any ice giant other than loki is evil apparently *eyeroll))
meanwhile, loki ((a magician- not an athlete lol )) also collapsed from nonstop running- and got raped by a sexually frustrated stallion. Then loki came-to, his female mare form was with foal. Loki remained in mare form to rear the foal Sleipnir and did not change back until the foal was of age to part from him.