This optional rule makes it easier for a creature to be felled by massive damage. When a creature takes damage from a single source equal to or greater than half its hit point maximum, it must succeed on a DC 15 Constitution saving throw
or suffer a random effect determined by a roll on the System Shock table. For example, a creature that has a hit point maximum of 30 must make that Constitution save if it takes 15 damage or more from a single source.
|1||The creature drops to 0 hit points.|
|2-3||The creature drops to 0 hit points but is stable.|
|4-5||The creature is stunned until the end of its next turn .|
|6-7||The creature can’t take reactions and has disadvantage on attack rolls and ability checks until the end of its next turn.|
|8-10||The creature can’t take reactions until the end of its next turn.|