2020-06-23 : Chandra's Incinerator counts all noncombat damage dealt to your opponents, not the difference in their life totals since the turn began. For example, if an opponent was dealt 5 noncombat damage but gained 3 life, Chandra's Incinerator still costs just {R}.

2020-06-23 : Combat damage is the damage that's dealt automatically by attacking and blocking creatures. Any other damage is noncombat damage, even if it's dealt during a combat phase by an attacking or blocking creature.

2020-06-23 : In a multiplayer game, Chandra's Incinerator counts damage dealt to opponents who have lost the game.

2020-06-23 : The cost reduction applies only to generic mana in the cost of Chandra's Incinerator. It can't reduce the {R} requirement.