how to tell if a pokemon card is rare know Pokémon & Valuable in 6 Steps What are the rarities of

If you've never seen Nadu in action, its ability (revealing the top card of your library whenever one of your creatures becomes a target of a spell or ability, then putting it into play untapped if it's a land or putting it into your hand if it's not, twice each turn for each creature) creates not infinite but sort of functionally infinite loops with an equipment that equips for free, like Skullclamp or Lightning Greaves

Please consider them all together

You might be wondering, what exactly are these 151 Master Ball Cards? To answer your question, these are actually the new and extremely rare Master Ball Mirror cards, only found in 151

It also has a unique move effect that reflects this emphasis on types

The window to acquire these at reasonable prices may not last forever