Mary rode up on what looked like a large, shaggy horse, and it took Wolfe a moment to realize that it was Pup, under the influence of some spell designed to increase his size. With [Detect Hidden], he could see the magic on the horse-sized dog, but that was as much as he could tell. Unlike an Elemental inscription that lingered while the spell was in effect, witch magic and potions just showed lingering signs of magic use.
"It's a potion of Giant Growth. He will revert back to normal size in a few hours, but for now, he's large enough that the wandering monsters don't attack us, and it's much quicker than travelling on foot.