I'm already not too hot on reusing "baby Pokemon", which is already an established and official term, but confusing it further by now referring to rarity with it is plain unnecessary
Oath of Nissa naturally limits the number of enchantments you can play before it threatens to miss, but you were never looking to go that deep, and cards like Courser of Kruphix obviously help your density of enchantments without cutting into your Oath of Nissa hits
The other, Malach of the Dawn is from Planar Chaos , a set designed to showcase alternate realities in Magic an apt place for one of Magics only male angels
Necron Dynasties has cards that care about when artifacts enter the battlefield, when artifacts die, when artifacts are milled, and when artifacts leave the graveyard
This is one of those ideal multiplayer cards as nobody wants to murder a 1/1 flying creature, but by the time it's a 7/7 flying creature, it's just a vampire bomb waiting to go off