Rubber Cement

Rubber Cement is a treasure card added to the game through the Four Souls + expansion pack. It allows the player to do a dice roll after missing an attack, and dealing one damage to any player or monster on the board on a 1-3 roll.

Special interactions
If the player were to receive lethal damage upon missing an attack, and then roll a 1-3 activating Rubber Cement's effect, and kill of the monster he was fighting, both the player and the monster would die at the end of the stack resolve. This is due to the fact that the monster dealing damage gets put on the stack the moment the player has missed his attack. Rubber Cements effect would be put at the top of the stack, thus it would resolves, which means the monster dies first, although the damage dealt to the player doesn't get removed from the stack.

the cement would hit before the attack resolve, it triggers on a miss and the monsters damage would be on the stack but the cement roll would need to resolve first. --Taken from Edmund McMillen's twitter post from 9th of January 2019 (UTC), 19:34