Kalemne’s third Planeswalker ability at level 60 creates a Greater Giant’s Triumph token that reads:
“When a creature you control with base cost 14 or greater attacks: It deals damage equal to its power to the opponent’s Planeswalker and to the first opposing creature.”
The Flash ability reads:
“Before your opponent’s creatures attack, if this card is Disabled, you may cast it.”
I almost lost a match on The Colossal Tussle today because even though Bedevil has flash and it should activate before my opponent attacks and therefore before the Greater Giant’s Triumph token activates its ability, it still dealt damage to my Planeswalker. After that I was able to cast Bedevil and destroy Greg’s creature. I don’t remember if it hit my first creature because it was Brash Taunter so it had prevent damage and it didn’t die.
Please correct me if I’m wrong but if the wording on the cards is correct, flash cards should activate prior to the Greater Giant’s Triumph token.