You can make a contract or summon a giant wolf, if it were by contract with the animal or summoned, it would be the size of the twilight wolves, which also have horses, and the wolf could be all black and with red eyes.
Unfortunately, summons are only people. Not Beasts.
It would have been great if MC could summon people. He would have summoned 5 dragons with top quality.
if war of the five king happens i hope mc follow rob stark to the south help him like preventing rob marriage to jayne westerling because i see many fanfic where mc remains in north and let rob die in the south.