You can't run away from it once you've been caught, however you can avoid being caught in it by simply walking around the sides (do NOT run).
in the desert resort
at the end of it
In relic castle
fossil in relic castle
It can be found in the Relic Castle in Pokemon Black Or White
Yamask can be found in the Relic Castle.
Relic Castle after you beat the Elite Four.
Relic Castle Catacombs in the wild. You have a 15% of finding it.
it is in the desert near relic castle
its at the very end of relic castle it is VERY hard to find:(
The Relic Castle is on route 4 where you have to go left and then up again.
You don't. Archen comes from a plume fossil, obtained in Relic Castle.