If you find yourself on Route 12 when playing Pokemon X Y, you are likely heading over to do battle with Ramos, the gym leader of Courmarine City. If you are heading down Route 13, then you are most likely on your way to fixing the Kalos Power Plant to fight Clemont, the gym leader of Lumiose City.
Either way, there are some valuable Pokemon to capture on both of these routes. 12 is bustling with a variety of them and 13 has only three observed quality Pokemon.
This route is a pretty big one and it has a farm at which you can ride Skiddo. There are some items you can reach if you look around for them.
On route 12, you are going to meet Miltank, Chatot, Pachirisu, Heracross (Y only), Pinsir (X only), Exeggcute, Slowpoke, and Tauros. Miltank is a normal type, Chatot is normal/flying, Pachirisu is electric, Heracross is bug/fighting, Pinsir is bug, Exeggcute is grass/psychic, Slowpoke is water/psychic, and Tauros is normal.
You will be most likely to encounter Miltank on this route. For every four encounters I had, half or more were Miltank. Bring some empty jars: you’re never going to buy milk again.
Update: harzilla from Tumblr has informed me that you can also find wild Mareep, the electric type, on Route 12; the catch is that they only appear in horde battles. Count each one you KO and maybe you can snooze as easy as a Snorlax.
Christopher_2176 has informed me that using surf will grant you an encounter with Tentacool.
This route is possibly one of the most annoying points in Pokemon X Y due to how large of an area it is and how little variety there is in the Pokemon. It is valuable, however, for when you go against Clemont, the electric type user, as the wild Pokemon on this route are all ground related.
You will find Dugtrio, Gible, and Trapinch. Dugtrio is mono ground along with Trapinch. Gible is a dragon/ground type.
Update: Accoding to Christopher_2176, you will find Graveler here by smashing the rocks.
There is one pretty cool thing about this route and it’s that the encounters involve the Pokemon coming at you from under the ground. There is a story reason for this that you will find out when dealing with the Kalos Power Plant. This route also has some sweet rails to grind on..
Need more help with your game? I’ve got you covered with Professor Neckbeard’s Pokemon X Y Walkthrough.