Mega Evolve

Mega pokemon are somewhat hard to find due to having to find mega stones.

Mega pokemon
Mega pokemon are the third or second form of pokemon but mega stones are required.

for example, if your trying to find a Alakazamite, you'll have a hard time due to have to wait a certain amount of time and get the upgrade and go deep in reflection cave.

Trivia
some pokemon can't mega evolve.

some mega stones are only found x or y. for example, tyrantarite is only found in X and Houndoomite is only found in Y.