Something wierd happened today: 2 chaos players, 1 against the other.
Now, the first uses Blessings of tzeentch, whose most recent description ( I think) is: sacrifice a unit. If you do bla bla bla.
In response, the 2nd player plays 1 of the 100 cards that deal damage, killing the unit declared sacrifice.
So, the question is: When do you select the target of a card? when it resolves or when it is played and it´s cost is payed?
To clarify, in this particullar case, can/must the 1st player sacrifice another unit?? Or does is the Blessings card simply discarted because the selected target is "no longer a valid target"??
Thanks in advance