These cards are essentially to summon synchro monsters, and their level is often important because players need to use monsters with levels that add up to the synchro monster's level to summon the card
Aside from being a human, which is a very relevant creature type in Commander, Modern and basically every other MTG format, Esper Sentinel is good because it reads: Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays X, where X is Esper Sentinels power. Its a bit like Rhystic Study, but the cost can be far higher if youve got things that make humans stronger or you can put +1/+1 counters onto Esper Sentinel
EDHREC's Paul Palmer had my back in his Sonic the Hedgehog deck tech, though, coming up with the idea of using The Seriema to tutor for her then leveraging her ability to allow you to tap your board to station the Spacecraft
If you design a card that you think would be fun, its more likely to do better
![]( 5 Likes lamplamp January 9, 2019, 10:45pm 5 I was like 8 or 9 when Base Set was released
The number of duplicate cards and Shinedust you need to add a Flair depends on the rarity of the card