Alternate Unconscious/Death Rules

Light Rules
These rules are to make the line between alive, unconscious, and death slightly more realistic, but don't change much in terms of game balance. They do not make it much easier or harder to die.

When a creature falls to 0 hit points, they are must immediately make a DC 10 CON saving throw.
 * On a failure, they fall Unconscious, prone and fail 1 death saving throw.
 * An unconscious creature that is brought to positive hit points must spend their following turn regaining consciousness. On that turn, they may stand up (if able) but cannot take any actions or bonus actions.
 * On a success, they are Downed.
 * A Downed creature falls prone, their movement speed is reduced to 10 feet, they lose concentration on any spells or abilities, and they cannot take actions or bonus actions (they can still take reactions). They cannot stand up unless supported by another player.
 * They continue to make death saving throws at the beginning of their turn as normal. When they fail a death saving throw, they must make another DC 10 CON saving throw. On a failure, they become Unconscious.
 * If a creature is brought back to a positive number of hit points, they are no longer Downed. If they are made stable (such as by the Spare the Dying spell), they are still downed but no longer have to make death saving throws.

Last Stand
When a creature is Downed and fails their last death saving throw, they may choose to make a Last Stand. A Last Stand may last for up to 2 turns, during these turns, they: At the end of the 2 turns, or if the player falls unconscious by any other means, they die. They cannot be resurrected by the Revivify spell.
 * Lose the effects of being Downed.
 * May regain the use of one expended ability that would normally only return on a short or long rest (including a single spell slot of 7th level or lower).
 * During particularly heroic Last Stands, DMs are encouraged to allow their players additional benefits as they see fit.
 * In certain moments, a player may wish to utter some final words before their passing. A creature that is being actively healed, or is brought above 0 hit points during their last stand may cling to life for up to 1 minute. At the end of that minute, they succumb to their wounds and expire.

Heavy Rules
These rules make the line more realistic, in addition to making going to 0 hit points feel more impactful. Too often in games falling unconscious isn't treated as the life-threatening or impactful event it should.
 * Creatures may enter negative hit points. If their negative hit points ever exceeds their maximum hit points, they die.
 * Death Saving Throws do not reset after being brought back above 0 hit points. They are instead reset upon completion of a short or long rest. If a character is resurrected, one of their failed death saving throws is reset.
 * When a creature falls below 0 hit points, they are must immediately make a CON save against their current hit points. The DC is equal to 10 or half their negative hit points, whichever is higher.
 * On a failure, they fall Unconscious, prone and fail 1 death saving throw.
 * An unconscious creature that is brought to positive hit points must spend their following turn regaining consciousness. On that turn, they may stand up (if able) but cannot take any actions or bonus actions.
 * On a success, they are Downed.
 * A Downed creature falls prone, their movement speed is reduced to 10 feet, they lose concentration on any spells or abilities, and they cannot take actions or bonus actions (they can still take reactions). They cannot stand up unless supported by another player.
 * They continue to make death saving throws at the beginning of their turn as normal. When they fail a death saving throw, they must make another CON save (DC 10 or half their negative hit points, whichever is higher). On a failure, they become Unconscious.
 * If a creature is brought back to a positive number of hit points, they are no longer Downed. If they are made stable (such as by the Spare the Dying spell), they are still downed but no longer have to make death saving throws.

Last Stand
When a creature is Downed and fails their last death saving throw, they may choose to make a Last Stand. A Last Stand may last for up to 2 turns, during these turns, they: At the end of the 2 turns, or if the player falls unconscious by any other means, they die. They cannot be resurrected by the Revivify spell.
 * Lose the effects of being Downed.
 * May regain the use of one expended ability that would normally only return on a short or long rest (including a single spell slot of 7th level or lower).
 * During particularly heroic Last Stands, DMs are encouraged to allow their players additional benefits as they see fit.
 * In certain moments, a player may wish to utter some final words before their passing. A creature that is being actively healed, or is brought above 0 hit points during their last stand may cling to life for up to 1 minute. At the end of that minute, they succumb to their wounds and expire.