ace spec card pokemon S&V - Temporal Forces NM RARE Holo Tool #154/162 MAXIMUM BELT Pokemon ACE SPEC Cards Guide:

The EX Pokemon were already going on for a while and kids knew they were really strong, but to have an even stronger version of that, I think that got a lot of people excited. 2

If you took this card as a face-down Prize card during your turn, before you put it into your hand, you may attach this card to 1 of your Pokmon.

Even if that is not the case, players are unlikely to want a full stack of commons for one higher rarity card, unless they are seeking to make a very shiny flair

Plane - Ravnica Grixis Blue, black, and/or red creature cards in your graveyard have unearth

It was also part of a vertical morph cycle in blue (Lumithread Field, Zoetic Cavern, Whetwheel) which all stayed in the file