Best for Gameplay: Format-warping spells like Force of Will (Legacy) and Ancestral Recall (Vintage) are considered "best" because they force opponents to build decks specifically to answer them
Rot-Curse Rakshasa $10.75 Rot-Curse Rakshasa is very interesting as a one-shot demon
In terms of naming and effects, its fine
Antiquities, 1994: $10,391 Antiquities was a very small set of 100 cards, and almost all of them are more than $1
If the proposed spell is illegal, the game returns to the moment before the casting of that spell was proposed So to answer your question, if - including X - the CMC of the spell is even, then it won't be allowed to be cast
Engineered for Magic: The Gathering These sleeves are more than just striking art