Pokemon TCG Pockets mechanical answer to this is flairs
This is due in part to its characteristic rage-fueled battles and its association with memorable in-game moments, such as its role in the Pokmon Stadium games, where it flexed its muscles in tournament battles
Now, it could easily be worth over $15,000
Once it hits the field, The Legendary Defender has a simple effect where if it attacks and destroys a DARK Fiend owned (not controlled) by your opponent, you win the duel
You can mark cards as owned and the deck builder will flag which ones you need to buy, which is useful
(7/13/2018) If the artifact leaves the battlefield, Treasure Nabber doesn't nab it from the zone it moved to