Fleet Swallower

• WWizards of the Coast2017-09-29
  Official Ruling
  Fleet Swallower’s triggered ability can target any player, not just the player it’s attacking.
• WWizards of the Coast2017-09-29
  Official Ruling
  If two Fleet Swallowers attack, each trigger determines the top half of that player’s library separately. For example, if the target player has fifteen cards in their library, that player puts the top eight cards into the graveyard, then puts the top four cards into the graveyard.

Rulings via Scryfall