Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Return target nonland permanent to its owner's hand. If you have the city's blessing, you may put that permanent on top of its owner's library instead.
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Once you have the cityâ€™s blessing, you have it for the rest of the game, even if you lose control of some or all of your permanents. The cityâ€™s blessing isnâ€™t a permanent itself and canâ€™t be removed by any effect.
If your tenth permanent enters the battlefield and then a permanent leaves the battlefield immediately afterwards (most likely due to the â€œLegend Ruleâ€ or due to being a creature with 0 toughness), you get the cityâ€™s blessing before it leaves the battlefield.
If you have the cityâ€™s blessing and choose not to put the target nonland permanent on top of its ownerâ€™s library, itâ€™s returned to its ownerâ€™s hand.
If you control ten permanents but donâ€™t control a permanent or resolving spell with ascend, you donâ€™t get the cityâ€™s blessing. For example, if you control ten permanents, lose control of one, then cast Golden Demise, you wonâ€™t have the cityâ€™s blessing and the spell will affect creatures you control.
If you cast a spell with ascend, you donâ€™t get the cityâ€™s blessing until it resolves. Players may respond to that spell by trying to change whether you get the cityâ€™s blessing.
A permanent is any object on the battlefield, including tokens and lands. Spells and emblems arenâ€™t permanents.