Key to the Archive
I believe you should take a look at Key to the Archive. In addition to its ability to break the color identity deck building restriction, the ability to draft an efficient win condition like Approach of the Second Sun is problematic.
The decks I've encountered have many ways to draw Approach of the Second Sun either the next turn or the one after that. Unless you have counter magic or you cannot win and this puts a serious timer on the game. Consider Shanna, Purifying Blade which draws cards like crazy...
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TapCastWin#12295 commented
I would also like to add that, Key to the Archive allows you to use cards in Historic Brawl that are banned in Historic Brawl (Demonic Tutor)...what is the point of this? From a strategy perspective, you SHOULD run this card in every deck...and that's a problem. I understand that I am choosing to make my deck worse by not running this card
It is mana ramp, it has tutors, it has wincons, it has removal, it has extra turns...