Playing Modified Brawl and opponent cast their commander Sauron, The Dark Lord, which has "ward- Sacrifice a legendary artifact or legendary creature". I attempted to counter the spell with essence scatter, which should be able to counter irrespective of the ward cost, since Sauron is still a spell while it's on the stack. Instead, a warning message appeared, saying my Essense Scatter would be countered unless I pay the ward cost. This is incorrect. I proceeded through the warning message, and was not given the chance to sacrifice my Baral (a legendary creature that was on the battlefield). This is also incorrect. I then used Brazen Borrower to return Sauron to my opponents hand, and sacrificed Baral to pay the word cost to do so (expected). My opponent then played Sauron again, and I used another counter on it, which resulted in the same ward warning and caused my counter to be countered by Sauron'snward ability. To reiterate: ward should not apply to a spell on the stack- only to a permanent once it resolves to the battlefield.