Yes, Cards from Mega Evolution Ascended Heroes follow standard Pokmon TCG rules and will be legal based on format rotation at the time of release
You can click the Get Items Authenticated Now ' button at the top right of this page to start, or download LegitApp on iOS or Android to authenticate your Pokmon cards anytime.
You don't have to lose a card from your opening hand like Gemstone Caverns
Protection from everything might not mean much on a 10-drop creature like Progenitus, but granting that same level of protection to a player for a full turn cycle is down-right silly, and exactly the reason you see The One Ring in just about any format where it's [questionably] legal
The biggest reason is just that you are spending mana to trade for cards from their hand
This can be done once per turn (including if you place new Pendulum Monsters in there), and Summons as many monsters you want as possible from your hand, or face-up Pendulum Monsters from your Extra Deck (more about that later)
