Nice and I think good balanced card.

But the wording needs some adjustments:
The second ability is weird with this wording, because you would cast the particular card from the graveyard. This is not impossible, but usually you just exile them (and then put the rest into the graveyard or shuffle them back). Also milling is more a blue-black thing instead of white-blue.

These are alternatives:
1. "Exile target non-land permanent. Its controller exiles cards from the top of his or her library until he or she exiles a non-land card. Until end of turn, that player may cast that card without paying its mana cost and as if it has flash. He or she shuffles all other cards exiled this way into his or her library."

2. "Exile target non-land permanent. Its controller reveals cards from the top of his or her library until a non-land card is revealed. Until end of turn, that player may cast that card without paying its mana cost and as if it has flash. That player puts all other cards revealed this way into his or her graveyard."

3. "Exile target non-land permanent. Its controller puts cards from the top of his or her library into his or her graveyard until a non-land card is put into the graveyard this way. Until end of turn, that player may cast that card from the graveyard without paying its mana cost and as if it has flash."


The ultimate ability wouldn't do anything at all even with this wording. Triggered abilities always happen after the event happened, which trigger the ability. That means the card is already drawn and then you would scry.
What you need is a replacement effect:

"If you would draw one or more cards, (you may) instead Scry X, where X is the amount of cards you would draw. Then draw X cards."
You can remove the may part, because I don't think it is needed and the ability text is already long (and you probably always want to do that anyway).

My idea for the second ability wasn't to mill. It's more to get a card to replace the one that was destroyed. It's meant to be a calculated risk. "Do I exile this card and hope that whatever my opponent gets is easier to manage?" Conversely, you could cast it on your own cards to exchange them for ones you know/hope are coming (presumably because you Scry-ed ahead of time).

The only reason they're in the graveyard as opposed to being exiled is that it's not supposed to counter strategies that rely on the graveyard. I struggled a bit with the wording, but even though it's not the best way to word it, I'm glad you were able to see where I was going with it. :)

Thanks for the critique. This is my first custom card, and I'm glad you like it.

You would'nt counter them. You don't take the cards the opponent has available, at least not directly. Actually right now you would do graveyard decks a huge favor when you mill their cards for them (well, at least when they have Crucible of Worlds or similar in their decks). The way the ability works so far you would mill land cards, however not many, I would guess 2-3 cards every time you use the ability.
You can prevent the graveyard problem with shuffling the cards back or put them under the library (maybe in a random order) like Possibility Storm does, but this may disrupt your control over your library you get with scrying.
If you put the cards back to the library it wouldn't affect the graveyard matters player at all, so that you don't have to think about that when you exchange the permanent card.

btw. I forgot that the wording of the flash part is actually different, too: "...that player may cast it as though it had flash."

Hmm. Those are some interesting idea. I'll keep that in mind, because designing my own card was too fun not to do again. XD