I definitely see this being played in a control deck to make sure you never deck out, and it might be better than Pidgeot V [Lost Origin] because you can use it from the Active Spot or the Bench
These cards work exactly the way you asked, you cast one half of the card for the casting cost, get that effect and the whole card goes to the graveyard
And why has it proven immediately unpopular
If you cast Mind Control targeting the relic, as soon as the Relic falls under your control, it stops being a creature, and therefore, Mind Control can no longer enchant it
Its worth mentioning that there will be an extended bonus sheet for Avatar (under the Eternal-Legal set code: TLE rather than the main sets TLA), but none of the cards have been revealed so far, and neither have potential special guests that have been known to be included with each set, which started with The Lost Caverns of Ixalan
------------ Club Members ------------ Amanda Deck: Lovely Friends Prizes: 3 Booster Pack: Mystery (x2) Amanda can be difficult