a Pokemon with a good ground type move like earthquake
Candice
you need to defeat pastoria city's gym leader
you need regice, regirock, and registeel in your team when you fight him
in heartome city but you need to find the gym leader
you need to cacth dialga first
you need at least one flying Pokemon or a psychc. gym leaders Pokemon are machoke fight,meditie fight psychc, lucario steel fight. im am pretty sher thos are her Pokemon
you can get him and fight him you need to go through mt.corenet and find your way to the spear pillar and there you'll find him.
You need to become the champion then when you enter the gym leader will say that she had a word with Cynthia and that you can go in
you need to use a strong fighting type like a lucario or medicham
If you play Diamond or Pearl,I'd recommend using grass-type Pokemon or your toughest Pokemon.Hope I helped!
you need to go to lake acuity and if you did you need to go to spear pillar.
You need the Mauville badge, go to Mauville and fight the gym leader, but you must first fight Wally to get to the door open.