Chameleon Blur

Where Fog wipes out combat damage for the turn (all combat damage, both ways, for a single green mana), this draws the boundary differently: it erases every point of damage creatures would deal to players for the whole turn, but only to players. The trade is right there in the wording. It will not save a planeswalker, will not blunt a Lightning Bolt to the face, will not touch a noncreature source, and it does nothing to protect your own creatures in a brawl. What it does cover is broader than a Fog in one direction and narrower in another: a second wave of attackers from a vigilant or hasty board, a creature's tap-to-deal-damage ability, a ping trigger that fires outside the combat step, all of it zeroed if the source is a creature and the recipient is a player. The four mana buys that turn-long, multi-source coverage rather than the one-shot combat blank. Instant timing is what makes it an answer rather than a tax: hold it open, let the opponent commit attackers and burn their activations, then erase the lot after the decisions are locked in. It is a deliberately bounded effect, written to never become a Fog-lock engine on its own, but the boundary is the source-and-recipient clause, not the combat step.