Wayward Swordtooth

• WWizards of the Coast2018-01-19
  Official Ruling
  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 one, then cast Golden Demise, you won't have the city's blessing and the spell will affect creatures you control.
• WWizards of the Coast2018-01-19
  Official Ruling
  A permanent is any object on the battlefield, including tokens and lands. Spells and emblems aren't permanents.
• WWizards of the Coast2018-01-19
  Official Ruling
  If you cast a spell with ascend, you don't get the city's blessing until it resolves. Players may respond to that spell by trying to change whether you get the city's blessing.
• WWizards of the Coast2018-01-19
  Official Ruling
  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.
• WWizards of the Coast2018-01-19
  Official Ruling
  Wayward Swordtooth's middle ability is cumulative if you control more than one. It's also cumulative with other effects that let you play additional lands, such as the one from Enter the Unknown.
• WWizards of the Coast2018-01-19
  Official Ruling
  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 of your permanents. The city's blessing isn't a permanent itself and can't be removed by any effect.
• WWizards of the Coast2018-01-19
  Official Ruling
  Ascend on a permanent isn't a triggered ability and doesn't use the stack. Players can respond to a spell that will give you your tenth permanent, but they can't respond to getting the city's blessing once you control that tenth permanent. This means that if your tenth permanent is a land you play, players can't respond before you get the city's blessing.

Rulings via Scryfall