Gamblers Sacrifice

You have a knack for helping others and are willing to take risks in the most dire of circumstances. You gain the following benefits:

Increase your Constitution score by 1, to a maximum of 20

• Once per day you may sacrifice any amount of your hitpoints to heal 1 other creature.  This exchange is typically of equal value.  For every hitpoint you lose, another creature will heal an equal amount of hit points.  This can not heal a creature above their hitpoint maximum.  After you declare the hitpoints you are sacrificing, roll a D20. 
• On a 20, you find yourself able to double the amount of hitpoints you heal without losing any extra hitpoints. This doubling can be split between 2 creatures instead of 1.
• On a 1, you take double the declared amount as a loss of hitpoints. The creature being healed only heals the originally declared amount.  If this would reduce your hitpoints to 0, you fall unconscious and take an immediate fail to your death saving throws.
• This resets at dawn each day.