I love the implication that Ertai couldnt find a familiar that suited him so he just magic-ed up an illusion of one that he could customize
The ETB creates a white and blue Knight with vigilance (the Knight creature token that shows up in the set), and the back is an enchantment that buffs your team
Having access to this with cards like Sythis, Harvests Hand in the command zone means you cast an enchantment, draw a card, the enchantment enters, and you can play a land from your hand
As noted earlier, the cards weren't initially perceived as collectibles
See, I was manipulated, had something of mine stolen, denied Aaron, and eventually will have my check from him bounce -- all characteristics of the color blue