SpoilerWhoops, didn't notice the encounter roll. Responding to your roll of 102 (!) now.
You and your Pokemon travel along the grassy plains unimpeded until just before noon, when all of a sudden, you hear the sound of hooves behind you. When you wheel around, all you see is a black-and-yellow blur traveling around you in a circle. While you're trying to follow it with your eyes, a second blur appears as well! The clattering of hooves suddenly stops as one of the twin blurs forms into a solid object in front of you and the other one stops behind you.
The best way to describe them would be...half yellow horse with white antennae and half black...animated tail. They look strange.
At any rate, their loud stamping hooves make it clear they're looking for a fight!
SpoilerMap!
They've used Agility on their first turn, it's your move now. Standard battle rules. OOC heads up, they're level 20+