Kindred Dominance

• WWizards of the Coast2017-08-25
  Official Ruling
  You can't choose multiple creature types, such as "Cat Warrior." A Cat Warrior is both a Cat and a Warrior. It's affected by anything that affects either type and unaffected by things that affect non-Cat or non-Warrior creatures.
• WWizards of the Coast2017-08-25
  Official Ruling
  Once Kindred Dominance begins to resolve, no players may take other actions until it's done. Notably, players can't try to save their creatures after you've chosen a creature type.
• WWizards of the Coast2017-08-25
  Official Ruling
  You must choose an existing creature type, such as Vampire or Cat. Card types such as "artifact" can't be chosen.

Rulings via Scryfall