Abyss Watchers

Double Strike, Vigilance, Indestructible.
When this card enters the field, create two 3/3
Knight Shade creature tokens with First Strike.
If no Knight Shade tokens are on the field,
this card gets +3/+0 and loses Indestructible.
Whenever this attacks, if a Knight Shade token
is on the field, defending player creates a
3/3 Knight Shade token.