As a land, it can't be countered, and it offers permanent card draw potential, even if you have to discard three cards after drawing just two
Legendary Creature Enchantment - God Erebos, God of the Dead Indestructible As long as your devotion to black is less than five, Erebos isn't a creature
The boost you get from countering a two or three drop and jumping to five or six on your next turn is a much greater swing than countering a four drop and then having 8+ mana for the main reason that you don't have that much useful to spend that kind of mana on very often and if you do it is not as significant as an earlier mana boost
Doom wont help you against fliers or if youre low on life, but in other scenarios, itll stabilize the board nicely
In gameplay terms, Donquixote Doflamingo doesnt do anything particularly fancy allowing you to set 2 DON
This is called setting the scheme in motion . Heres a few examples of what might happen