Detective of the Month

Once you have the city’s blessing, you have it for the rest of the game, even if you lose control of some or all your permanents. The city’s blessing isn’t a permanent itself and can’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 “legend rule” or due to being a creature with 0 toughness), you get the city’s blessing before it leaves the battlefield.

If you control ten permanents but don’t control a permanent or resolving spell with ascend, you don’t get the city’s blessing. For example, if you control ten permanents, lose control of two, then cast Detective of the Month, you won’t have the city’s blessing.