you sould go underground there are thunder stones down there
the Pokemon that evolve with the help of a thunder stone are : pikachu +thunder stone = raichu, or eevee + thunder stone = jolteon.
after you beat Cyrus in veil stone city
thunder Pokemon if it has evolutions
You can find the thunder stone in New Mauville
you can find a thunder stone by checking the UNDERGROUND
Pickachu and eeve can evolve with the thunder stone
You can't, it needs a Thunder Stone.
thunder stone
pikachu
A Thunder Stone is an evolutionary stone that allows certain Pokemon to evolve when exposed to it. In the third generation of Pokemon games, there is one Thunder Stone in New Mauville, and they can be had from the Diving Treasure Hunter for Yellow Shards.
Pikachu and Eevee both need a Thunder Stone to evolve.
PIKACHU