Blue demon.

I don't think this comes as a surprise for you, but I'm quite certain that this is busted. There's no way 'draw fifteen at next end step' for would be balanced in this manner. I would consider adding some additional ability such as limiting it so that you can only cast one spell per turn and/or exiling all cards you would put into your graveyard.

Mmm, I'm not so sure. It needs some setting up (Library of Leng, Vedalken Orrery) to really make use of. Though it's also hilariously funny to give it to an opponent who isn't ready for it...

It's certainly powerful. But it's definitely something that can exist.

Is it too cheap? Probably. But it's certainly fun and exciting. Solution? Give it a name, make it a mythic legend, and then people will play it in commander where it's HILARIOUS and also all concerns about power level go away because mythic excuses all undercosts forever. ( make it cost 5+, and it's fine. Make it cost 7 and it's underpowered, and could be 'player of your choice draws 15')

> It needs some setting up (Library of Leng, Vedalken Orrery) to really make use of.

I'm not sure what you are going about. Imagine if you had a sorcery with "at end of turn, draw fifteen (or basically any absurd number that's about roughly than 50)". It matters relatively little that the cards are drawn at end step in the grand scheme of things - you just refilled your hand entirely and got insane card selection in addition to that (and graveyard shenanigans). It's basically the same thing as with Jin-Gitaxias, Core Augur, but better and with - to mana investment. Getting rid of the demon itself is more of an afterthought on later turns if you somehow didn't get all of your winning pieces and more in your hand already (+ a 5/5 evasive beater isn't that shabby of a deal either). Your opponent absolutely has to have instant speed removal or counter spell for this or you just won the card advantage war with this single-handedly.

You are able to do crazy things in EDH, but even in that format there are still things that are hard-banned such as Griselbrand and Emrakul, the Aeons Torn. Mythic rarity didn't make them immune to the ban hammer.

That's a good point. Let's try this design:

Tahz: If you don't have some way to retain those cards; then you'll just be discarding them. And the large number of cards means decking yourself does actually become a concern.

Saying that - 4 was too cheap for the effect.

At 6 - this is interesting. Not being able to turn it off might occasionally be a drawback; but I think the opponent being unable to ever able to turn it off is just gonna be way too annoying.

But meh, it's a mythic that doesn't instantly win the game, it's cost high enough that vintage won't care about it, it gets a pass.

So far it seems that WotC has indicated that they aren't interested in using emblems for anything other than 'walkers (Praetor's Counsel and arguably the ascend mechanic are examples of this).

While this won't perhaps be a player in other eternal formats, I still think this is quite disgusting in EDH. There are just so many ways to make that 'drawback' a non-issue. Anything from Wheel of Sun and Moon, Obstinate Familiar, to a simple Elixir of Immortality just blanks the supposed decking chances. It's especially concerning that now there is no way for the opponents to interact with this once it hits the field.

From design standpoint I also dislike that the creature has been demoted to a mere bonus in addition to the effect and has no bearing on it whatsoever. It begs the question of why is this even a creature anymore?

I with Tahazzar- 15 cards no with no set-up is ridiculous. Why even worry about decking out when you're guaranteed to draw your win con? While having to wait to the endstep probably doesn't make it replace Griselbrand it's easy too breakable in edh.