Being able to copy any spell you control for just one mana is an exciting rate, considering the same ability on Lithoform Engine costs four mana (although it is worth mentioning that Overloaded Mage-Ring is a one-shot)
The Reserved List is silly, and Magic is too expensive
In terms of design, Manaphy is inspired by marine life, featuring a blue, jellyfish-like body with large, expressive eyes that endear it to many fans
Finally, Thrasios, Triton Hero isn't exciting, but it's not really a bust either, essentially being a repeatable (but expensive) Coiling Oracle when it's on the battlefield
They all had the same type of cut (like the cloyster above), all were water type, all were from breakpoint, it all lined up
Dethrone is usually easy to trigger, and even without it, you can use other +1/+1 counter effects to make sure your creatures keep coming back