With relatively low base HP for a rare card of this type, Regirock is best used against those weak to Fighting attacks, such as Darkness, Lightning, and some Colorless pokemon cards
The same 20-year nostalgia cycle driving EX-era collectors back into the hobby is already well underway for Base Set, and Shadowless cards are sitting directly in the path of that demand wave
Its Super Zap Cannon move is a little hefty, requiring 2 Energy cards to be discarded from it to use and only doing 190 damage (which will rarely knock out a Pokemon)
It defends itself with a vast, impenetrable wall of ice
At this point, if you're planning to build Shrines in Commander there isn't really a lot to be done other than to bite the bullet and pay the new higher price
Her powers are far greater than those of her creations, having the ability to create life as well as manipulate time and reality itself