Many-in-One

Your single existence is shared with other Members. Each Member could be vastly different than the rest and can be considered a unique individual in their own right, but by virtue of your unique state, each Member is still part of a single Many-in-One.

Key Terms

This unique background makes use of some key terms for the sake of clarity and ease of play.

• Many-in-One: the collective name for the entire group of Members who share a single existence.
• Member: the individual term for each character that is part of the Many-in-One.
• Active Member: the current character in the Many-in-One who is in play.
• New Active Member: the subsequent character after a Switch.
• Inactive Member(s): all characters in the Many-in-One who are not being played. While inactive, for the purpose of rules interaction, it is as if they are dead, in stasis, and on another plane - though this may not actually be the case depending on the origin of the Many-in-One's Shared Existence.
• Switch/Switching: the process of one Active Member being replaced by a New Active Member.

Character Creation for the Many-in-One

The Many-in-One technically functions as a single character, except each individual Member has their own character sheet that you use while that Member is active. Each Member's character sheet has the following changes:

• Background. Your background is the same and shared by the Many-in-One, which means every Member has this same Many-in-One background.
• Suggested Characteristics. As this background does not provide any Suggested Characteristics, you may come up with your own or use the Suggested Characteristics of another background. You may decide whether each Member shares the same Suggested Characteristics or has different characteristics
• Starting Equipment and Gold. No Member receives any additional starting equipment from their class at character creation. You only get the equipment and gold from this background, though you may use the shared gold to purchase items.
• Other Character Creation Options. Since it is possible for Members to be of different ages, races, genders, appearances, levels, and so on (though they don't have to be), all other Character Creation options are not shared or the same. But, you may decide to share certain options and make them the same. Make sure your DM knows what additional options (if any) are shared/same.

Playing as the Many-in-One

Beyond Character Creation, the Many-in-One has the following rules:

Roll a Die to Switch, but Be Careful - It can be Disorienting!

At the start of every session, roll a die equal to the number of Members. This die determines the Active Member for that session. If there is no die for the exact number of Members, use the closest possible die; any extra numbers on the die can either mean you pick who is active, the DM picks who is active, or something else.

After a switch, the New Active Member must immediately make a flat DC9 check to simulate them orienting themselves or getting used to being the Active Member. On a failure, the New Active Member has disadvantage on all rolls, saving throws, and checks for 1 Round. This roll resolves before any other rolls!

You may work with your DM to discuss alternative ways to switch the Active Member or to adjust the default method. For example, there might be certain triggers that force a particular Member to switch into the Active Member; or the DM may decide to force a switch during particularly stressful moments or for narrative impact. This is something that should be agreed upon between the player and DM beforehand.

Inactive Members are Functionally Dead, in Stasis, and on Another Plane.

To clarify how things might resolve with Inactive Members, treat them as if they are dead, in stasis, and on another plane. Inactive Members might not actually be these things, and depending on the origin of the Many-in-One's Shared Existence, Inactive Members might still be reachable somehow.

While inactive, Inactive Members' stats are kept as they were the last time they were active with the exception of HP. For example, if a Wizard has used up all their spell slots while active, they do not regain them while inactive; the Wizard must regain their spells from resting as normal while active.

HP is Shared (but Cannot Exceed Max HP), so if One Dies, They All Die.

HP is shared between the Many-in-One, although Max HP and hit dice might differ. So, if the Active Member of the Many-in-One dies, the entire Many-in-One and all of its Members die. Additionally, the Active Member's current HP cannot exceed their standard max HP because of switching; the lower current HP overrides the higher current HP.

For example, if Member A (20 Max HP) switches with Member B (30 Max HP), Member B starts with only 20 HP but can regain HP thereafter to their normal maximum. But, if Member B (30 Max HP) switches with Member A (20 Max HP), Member A starts with only 20 HP since they cannot exceed their maximum.

Active Effects and Features are Resolved during a Switch, and Some Might Transfer.

When the Active Member switches, resolve all current effects and features as if the Active Member has died.

Effects and features that require the Active Member (such as concentration spells or abilities that break when the Active Member leaves a certain area) immediately end when the Active Member switches. On the other hand, effects and features that do not require the Active Member (such as Instantaneous spells, fixed duration spells, or an ongoing effect from a source outside the Many-in-One) transfer to each New Active Member as if they were the same character.

For example, if the Active Member is invisible due to casting and maintaining an Invisibility spell, the spell would immediately end upon switching and the New Active Member would appear. However, if the Active Member was invisible because the spell was cast by someone else, the New Active Member would remain invisible.

As another example, the bonus HP from the Aid spell would transfer from the Active Member to the New Active Member, even if it was the Active Member who originally cast the spell.

Conditions are Shared but with a New Saving Throw.

The Many-in-One shares conditions, but when the Active Member switches, the New Active Member receives a saving throw and resolves it using the New Active Members' relevant stats.

For example, if the Active Member was charmed by a vampire, then the New Active Member would get an immediate saving throw to break the charm.

All Equipment and Attunement Slots are Shared and Do Not Switch.

The Many-in-One shares all inventory, equipment, items, and attunement slots between the entire Many-in-One. They are the same for each Member, though magical items that magically resize themselves to fit a character will resize themselves to fit the Active Member.

Any equipment that requires a specific prerequisite or feature cannot be used unless the Active Member qualifies as normal. Attuned equipment remains attuned unless the New Active Member does not qualify - in which case, the attunement automatically ends as per normal rules.

How the Members of the Many-in-One Interact with One Another is the Player's Choice. 

Subject to the player’s choice, the memories and experiences of each Member can be automatically shared between the Many-in-One. By default, all Members of the Many-in-One advance together in level and character experience unless the player decides otherwise.

Related to this, the Members of the Many-in-One cannot communicate with one another normally since only one exists at a time. But, they might be able to communicate through magical means or through shared memories and experiences.

Adding or Removing Members of the Many-in-One

Generally, it's assumed that the Members of the Many-in-One remain static through the course of their adventures, but this isn't always the case. Whether due to magic, a major event, or something else, Members might merge, split, appear, or cease to be. Below are some ideas, but work with your DM to discuss ways to approach this. Remember to keep the gaming experience of all players at the table in mind.

• Members Merge. Individual Members might merge with other Members. A simple way to resolve this might be to have the player make a new character sheet that represents the merged individual while doing away with the former characters/sheets. This new character should probably be at the same level as the highest Member in the merger but no higher.
• Members Split. A single Member might split into other, new Members. To simulate the split, create new character sheets for each new Member at a character level at least one lower than the original Member. (In addition to simulating a split, the loss in character level is also meant to balance out the new flexibility from having more character sheets.)
• New Members Appear. Simply make a character sheet per each new Member and add them to the list of Members in the Many-in-One. New Members shouldn't exceed the highest leveled Member of the Many-in-One or the highest leveled character in the party (whichever is lower). The new Member does not bring in any gold, equipment, or items with them.
• Members Disappear. Members might cease to exist in the Many-in-One. In this situation, simply dispose of the relevant character sheet(s).