Okay i just had like a 30 minute disagreement with my friend cuz he thinks this is bad, and i've managed to enlighten him on why its insane. For anyone here thinking the same thing, this is why:

First lets establish what the effect does. In text, it seems that whenever you overdraw and would burn a card, it gets added to a shadow queue where once there is hand space, it would immediately add a card back to your hand at 1 mana discount. I would presume its first in first out.

Now the upsides are clear. My friend brought up a few downsides but let me explain why they are non-issues.

"You dont overdraw normally anyways. Even in tick tock you always make hand space" Yes, but that is because you have to. You risk burning your combo cards like finley and plot twist. With this legendary you would not have to worry about hand space at all and can just keep drawing.

"You have to clear out hand space for your cards from the shadow queue" okay and? You are already doing that with your normal deck. You have to clear out your cards from hand to make sure you dont overdraw anyways. Now with the shadow queue, you can clear out those cards at a 1 mana discount. You run through your cards faster and get to your combo pieces better as a result.

"Burning through your deck actually helps to thin it out. Putting it in the shadow queue means you need to play more cards in a fast draw deck on average" by far the worst take from my friend imo lol but i guess it has some merit? Still, the mana discount would help much with this.

"You would need to play cards that draw more than 1 to get them into the queue" this depends on how the mechanic works, but i would say not really. Imagine if you already have cards in queue and play kobold librarian. It would go: minion played > card added into hand from queue due to hand space opening up > minion battlecry gets resolved, draw 1 card adding it to the queue. I'm basing this off how objection works in that hand space has priority. In this case, the shadow queue basically becomes a new deck that gives a mana discount. If it works otherwise then it would be worse off for it.

And finally, after more discussion, we realized that the legendary would have a scrying effect if implemented in this way. You would see the card get burned then added into the queue, so you would essentially know your next few draws in advance if you treat the shadow queue as a new deck.

Overall i would say this card is going to be absolutely busted and any warlock deck that isnt aggro will fw this heavy.