He's almost a strictly better Murmuring Mystic, with a higher power and the Birds he makes having vigilance
Since the effect of this card is dependent on how many swamps you control, it functions best when featured in a mono-black deck
This is best with cards like Breya, Etherium Shaper that focus on building a wide board of artifact tokens to churn it out as cheaply as possible
My big picks for this deck are Sword of War and Peace and Molten Psyche, which can do some serious damage
The types and mana value of a double-faced card in exile are determined by the characteristics of its front face
As a Commander or part of any deck, Yuna, Hope of Spira works really well with all kinds of enchantments and some kind of mill/discard strategy that lets you get those expensive enchantment creatures into your graveyard so you can then cast them for free