In a deck with black creatures, and especially creatures like Blood Artist, the flip could be very costly to one of your oppokn For the front card, a cheap equipment will do if all you want is to satisfy the flip condition
Once Warden of the Chained is attacking, 'it will remain attacking even if you no longer control another creature with power 4 or greater
Well, that answer came in the form of an announcement article
If you cast Expedite targeting Zada, Hedron Grinder, Expedite gets copied targeting each other creature you control
The other side of Valki is a seven-mana planeswalker called Tibalt, Cosmic Impostor
The final reprint I want to highlight is Kodama of the West Tree , although this is also in the Jumpstart packs