Heres an example of what a Eureka deck might look like nowadays: Creatures (13) Planeswalkers (2) Lands (20) Spells (26) Even setting aside the Reserved List , Eureka would be pretty near the top of the list of cards never getting reprinted in a Standard-legal set
He focuses on affordable decks in Pioneer, Modern, and Pauper, particularly ones that stray from the mainstream
Braingeyser will let you refill your hand as needed at this point, and you should be able to generate infinite mana, infinite Shivan Dragons, or the opportunity to fire off infinite Braingeysers at your opponents
Hes one of the best mythic rare MTG cards for artifact strategies, and one creature doing all of that at four mana is why he dominates Commander
If an effect makes you discard a card and you dont have any, nothing happens
While I personally like direct removal spells, this can become useful in mono-blue decks that otherwise dont have reliable answers to threats