Avediel, Divided Devotee

When Avediel enters the battlefield choose Seraphs or Usurpers:
Seraphs -Whenever one or more creatures you control deal combat damage to a player, put an exalted counter on target land you control and draw a card. If only one creature attacked this turn, you may search your library for a basic plains card and put it onto the battlefield tapped.
Usurpers - Whenever one or more creatures you control deal combat damage to a player, mill 2 and draw a card. If only one creature attac