I have an eldrazi edh deck with Yidris, the maelstrom wielder. What would happen if I came across my Endless One? Would I cast him and he’d become an infinite creature since I casted him for free? And what is his converted mana cost? Would I be able to even cast him?
Sorry if the tag isn’t working this is my first post and I’m not sure I got it right :/
In general, if you cast a card with X in its mana cost due to cascade, the X will be 0; cascade won't let X be anything other than 0 (C.R. 702.84a, 107.3b). (Currently, the only exception is Spoils of War [C.R. 107.3c].) See also this thread.
So then endless one would just be cast onto the field as a 0/0?
You can cast Endless One due to cascade. However, since X will be 0 in your scenario, when Endless One resolves it will enter the battlefield with no +1/+1 counters on it (and go to the graveyard as a state-based action after that, if nothing else is affecting Endless One's toughness) (C.R. 608.3, 117.3b, 117.5, 704.5f).
Sorry if the tag isn’t working this is my first post and I’m not sure I got it right :/
EDIT (Mar. 18): Edited rule citations.