you have to beat the Canalave Gym leader. Then go to the library with your friend and you'll hear a big Boom then you'll be able to get past the people on route 213.
Route 213
Route 213,Route 218 and Route 222(morning.)
route 213 by the fence
you have to go to pastoria city and keep on going right past route 213 and you reach route 222 and then you get to the 8th gym leader's city.
In route 214 & 213. Their levels vary from 21-28
route 213 and battle frontier shop
Pastoria City, Sunyshore City, Pokemon League, Route 212, Route 213, Route 222, all by fishing with the Super Rod.
go to route 213 and use the super rod and you shoud get an octillary
You can find them at these places: Route 212 South, Route 213, Route 222, Route 223, Route 224, Route 230, Pastoria City, Sunyshore City, Pokemon League. (Fish with Good Rod.)
You can't catch a Taillow in Pokemon Platinum, but you could catch the later evolution (Swellow) using Poke Radar on Route 213, and then breed it to get a Taillow.
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There is one of two ways you can get an octillery. You can evolve it from a Remoraid at level 25. You can also catch one in Pastoria city, Sunyshore city, Pokemon league, route 212, route 213, route 222, route 224, route 223, and route 230.