These rules seem pretty common among groups of veteran D&D players.
BETTER CRITICAL HITS: On a critical hit, the damage is maximum damage plus another die roll instead of doubling dice. For example, a hit with a short sword would cause 6 + 1d6 + modifiers instead of 2d6 + modifiers.
INSPIRATION: Characters may expend Inspiration not only for their own rolls, but also to grant a re-roll to an ally character within sight, or force the DM to re-roll an NPC or monster’s roll. (Note the an Inspiration bonus roll is not the same as having Advantage or Disadvantage in terms of granting other abilities, such as a rogue’s Sneak Attack class feature.) “Sharing” Inspiration tends to help foster more player cooperation at the table.
POTIONS OF HEALING: Using an action to consume a Potion of Healing grants its user the maximum number of recovered hit points. If using a bonus action to consume the healing potion, roll for results. This one is practically canon at this point.
POWER-THROUGH FINAL BLOWS: If an attack downs a target (reduces it to zero hit points), any remaining damage may be applied to an adjacent target within reach if the attack roll meets or beats that target’s Armor Class. This rule may also be used for ranged attacks, but only against targets behind the first target and within the attack’s maximum range. For example, a sword attack roll of 14 hits for 10 slashing damage against a target that only had 7 hit points left. The remaining 3 hit points can be applied to another target of AC 14 or less that is within the attacker’s reach.
FAILED DEATH SAVES: A dying character’s failed death saves don’t reset until being healed above zero hit points. (This note is more a clarification than a house rule.)
DYING NPCS AND CREATURES: A non-player character or creature reduced to zero hit points is unconscious and automatically becomes dead in three rounds (as if a player character who fails three death saves). Any healing given to the dying NPC or creature will keep save its life.
MINOR CREATURE NOTES (from Reddit):
- Cats and lions have 60 feet of Darkvision, just like Tabaxi and tigers.
- Polar bears have cold resistance.
- Tortles live for an average of 150 years, not 50 years.
More experimental ideas…
BULLY TACTICS: As an action, a character can attempt a Charisma (Intimidation) roll versus one target’s Wisdom saving throw, or with disadvantage against a group (each making an Intimidation roll). Success makes the targets Frightened of the character until the end of their next turn. Alternately, Strength (Intimidation) may be used for feats of strength, or Wisdom (Animal Handling) to have a similar effect on beasts.
HIDDEN DEATH SAVES: Players roll them in an opaque Solo cup and cannot see the results until three rolls (three cups) are in front of them. After the third roll, the cups are removed and the current status is revealed: recovered, dead, or one away from either state. If any of the three rolls came up 20, the character recovers one Hit Die up from zero hit points.
DYING CONDITION: At zero or less hit points, a character gains the “Dying” condition instead of “Unconscious.” The character may crawl 5 feet per turn; cannot take actions, bonus actions, or reactions; and can only speak in a halting whisper. Death saves are made as usual.
FLASHBACK INSPIRATION USES: Besides re-rolling ability checks, saving throws, and attack rolls, Inspiration may be used for a flashback sequence. Under the player’s narration, the character is seen preparing a plan or double-cross that now lets the character find one specific non-magical item hidden nearby, gets one enemy NPC to secretly switch sides and help the party, or sets up some other specific advantageous situation. (Think in the style of heist movies.)
BLOODIED CONDITION: Creatures at half or less maximum hit points are obviously injured, noted by the “Bloodied” condition. (Borrowing the idea back from D&D4e.) To know exactly how many hit points a creature has, as an action an Intelligence (Medicine) check can be made within 5 feet, versus a Difficulty Class equal to the target’s Challenge Rating. The action can be made at a longer distance (up to 60 feet) with disadvantage.
DEVIL’S BARGAIN: Borrowing from the “Blades In The Dark” RPG, a player without Inspiration may gain a re-roll for a character’s ability check, attack roll, or saving throw in exchange for one of the following (chosen before the die is rolled again):
- For an attack roll, on a successful hit the character suffers the same amount of damage in return as caused by the attack. (The attacker twists a leg while striking, the target scores a counter-strike or crushed the attacker, or its toxic insides spray the attacker with goo, or some other harm occurs.)
- For an attack roll, a miss causes the character to drop its weapon (or spell focus if a spellcaster), requiring a bonus action to recover it.
- On a saving throw, any potential damage is doubled if the second roll also fails.
- The Dungeon Master gains one “Devil Die” to use as Inspiration for any NPC or creature met later in the adventure. (Unlike Inspiration for player character, the DM may rack up multiple “Devil Dice” but may only use one per turn.)
ALTERNATIVE CRITICAL HITS: On a critical hit, instead of causing double damage, a character may choose to duplicate the effect of Battle Master maneuver with an effective DC of 20 for any related saving throws. The effects may result from a weapon attack or a spell attack.
- DISARMING ATTACK: When you hit a creature with a critical hit, you can attempt to disarm the target, forcing it to drop one item of your choice that it’s holding. The target must make a DC 20 Strength saving throw. On a failed save, it drops the object you choose. The object lands at its feet.
- DISTRACTING STRIKE: When you hit a creature with a critical hit weapon attack, you give your allies an opening. The next attack roll against the target by an attacker other than you has advantage if the attack is made before the start of your next turn.
- GOADING ATTACK: When you hit a creature with a critical hit, you can expend one superiority die to attempt to goad the target into attacking you. The target must make a DC 20 Wisdom saving throw. On a failed save, the target has disadvantage on all attack rolls against targets other than you until the end of your next turn.
- GRAPPLING STRIKE: Immediately after you hit a creature with a critical hit on your turn, you can try to grapple the target as a bonus action (see the Player’s Handbook for rules on grappling). You gain advantage on your Strength (Athletics) check.
- MANEUVERING ATTACK: When you hit a creature with a critical hit, you can maneuver one of your comrades into a more advantageous position. Choose a friendly creature who can see or hear you. That creature can use its reaction to move up to half its speed without provoking opportunity attacks from the target of your attack.
- MENACING ATTACK: When you hit a creature with a critical hit, you can attempt to frighten the target. You The target must make a DC 20 Wisdom saving throw. On a failed save, it is frightened of you until the end of your next turn.
- PUSHING ATTACK: When you hit a creature with a critical hit, you can expend attempt to drive the target back. If the target is Large or smaller, it must make a DC 20 Strength saving throw. On a failed save, you push the target up to 15 feet away from you.
- TRIP ATTACK: When you hit a creature with a critical hit, you can attempt to knock the target down. If the target is Large or smaller, it must make a DC 20 Strength saving throw. On a failed save, you knock the target prone.