The following are a hodgepodge of random rulings and precedents the Dungeon Master uses, in addition to the official rules of the PHB/DMG and any other homebrew mechanics explained on this website. It is not necessary for a player to memorize (or even read) these to play; they are simply here for reference.
• Real life comes first. Attend sessions when you can, leave them when you must. The narrative will flow around you. (While you are absent, your character will simply become a “background character” that doesn’t interact with events but also is not affected by them.)
• Keep combat turns moving quickly. If you still need to decide your turn when it comes to your initiative, the DM can delay your turn until a later place in the order. Additionally, if the remainder of your turn involves choices that won’t directly affect the combat state (e.g. turning Sorcerery points into spell slots, wildshaping, most healing spells), the DM might pass your turn to the next player, letting you finish your turn in the background.
• Inspiration is awarded through a voting system. If at least four characters are without Inspiration at the end of a session, then a secret vote is tallied. Players vote twice, nominating any other player who either a) roleplayed in an inspiring fashion, and/or b) contributed meaningfully to the success of the group as a whole. (This allows players to contribute either as roleplayers or min-maxers.) The two winning players will receive Inspiration at the start of the next session.
• I will not kill off a Player Character, unless the player themselves wishes to retire them in a dramatic fashion. Players should be assured that their characters will survive long enough to warrant emotional and lore investment. That being said, poor decisions can still be punished, and there will be NPCs, missions, and objectives that can be easily lost.
• Feats and multiclassing are permitted.
• Flanking provides advantage on attack rolls (subject to change). From the DM Guide’s optional rules on flanking.
• Creatures must locate at least three-fourths cover in order to use the “Hide” action. This is based off the concepts in this article.
• Psionic abilities are considered arcane/magical/spell as per psionic/arcane transparency. An Antimagic Field, for example, would stop psionic effects. On the other hand, psionic effects that are cast via “innate spellcasting (psionic)” with no components whatsoever would be immune to Counterspell. This is based off the concepts in this discussion.
• A wildshaped Druid can cast spells as long as they are subtle spells via metamagic. It can be argued that, RAW, druids cannot cast spells through any means until level 18. On the other hand, the resources invested in granting a Druid access to subtle spells probably outweigh the added benefits.
• “Leomund’s Tiny Hut” only blocks magical effects that are “area-of-effect” or require direct line of sight. For additional protection against divination or teleportation, consider Mordenkainan’s Private Sanctum.
• Lower-level spells/abilities should not negate higher-level spells/abilities. For example, Detect Magic should not be able to see through Invisibility or Nondetection. (In the case of Invisibility, the nearby presence of magic is felt, nothing more; in the case of Nondetection, nothing is felt at all.)
• For difficult terrain, any extra cost for movement (and damage taken from spells like Spike Growth) only triggers when a creature enters the affected square, not leaves. Otherwise, you could get double duty from a single square.
New or Refined Game Mechanics
• Players may only “Help” with a skill check if they are themselves proficient in that skill. Much like a second player may only Help with Thieves’ Tools if they themselves are proficient with Thieves’ Tools, a second player may only help with lore checks (as an example) if they’re studied in them. (Otherwise, outside of combat, players essentially receive free Advantage on most skill checks.)
• Players may receive free lore skill checks in skills they are proficient in. For example, players proficient with Arcana (INT) may get a free roll during combat to recognize an Intellect Devourer, but only at DM’s discretion. (DCs are generally 10 + relevant CR.)
• In a similar vein, characters proficient in Arcana can make one free Arcana (INT) check per turn to identify a spell being cast, for the purposes of countering it. This costing a Reaction (as per Xanathar’s) makes no sense, since it also takes a Reaction to Counterspell.
• Players are allowed to delay their turn to later place in the initiative order. However, spells or effects that last to “end of your next turn,” for example, might fall off when this action is taken (DM’s discretion).
• Players may feed a potion to another player as a standard Action, even if the recipient is unconscious. As this is generally a poor use of action economy, I have no issue allowing it; and it can make the difference between life and death. (Let’s just say they…pour it down their nose, or something.)
• Players are not punished for casting spells while their hands are full, as long as they are proficient with whatever they are holding. As an aside, the “War Caster” feat is still useful for gaining advantage on CON checks to maintain concentration.
• Players can purchase scrolls of spells at higher levels than their “default” value. For example, a mage can purchase scrolls of Lightning Arrow at 3rd or above. (The scroll’s value is derived from the level of the final spell.)
• Inspiration can be donated to another player. As it’s a finite resource that slowly replenishes only between sessions, there’s no game balance reason it can’t be shared among the group.
• When leveling up, players may change out the highest level of a class for a new level in a different one (much like UA’s “Spell Versatility,” but for class levels). Player characters must have at least one uninterrupted month of downtime in which to train, and they may not swap out a class level if that level involves a prerequisite for another retained feature of their character. Spells learned are retained, even if the character is no longer capable of casting them.
• Spells like “Comprehend Languages” and “Tongues” only work on living languages of Faerûn. Dead languages, languages spoken only outside of Toril, and some occult languages like Deep Speech won’t be automatically translated. However, talented linguists can still parse the meaning with successful skill checks, such as with History (INT).
Adjustments to Stated Rules
• “True Strike” can also be cast on another creature via touch. All other elements of the spell remain the same. Again, not the best use of action economy, but it makes the spell playable.
• Rituals for Identifying Items (and similar) can do multiple items within the same time frame. Once the initial ten minutes for a ritual have been spent, there is no reason to punish the players for additional uses of it.
• The “Intimidation” skill uses a physical attribute as its base stat: i.e. Intimidation (Strength). Normally, Intimidation uses Charisma, which means it nearly replicates the Persuasion (Charisma) skill; changing it to a physical stat allows combat-oriented classes to contribute as well. While it’s most common to intimidate through sheer physical prowess, it’s also possible to demonstrate precision with knife throwing (Dexterity) or remain standing after a chair is broken across your back (Constitution).
• In keeping with the above, Persuasion (Charisma) can now be used towards any effect an Intimidation (Charisma) check would have accomplished. This means Persuasion might be used to either shift an NPC along the hostile-unfriendly-neutral-friendly-helpful scale, or to hurry them along in a specific course of action.
• “Crafting” an item or items can be automatically accomplished during downtime, as long as the character has proficiency in the related tools and an uninterrupted ten days. Since the campaign uses a wealth-by-character-level model for equipment, there’s no point in applying an extra time gate or penalty.
• When drowning or asphyxiating, instead of being able to hold their breath a number of minutes equal to one plus their CON modifier, players now have their CON modifier number of rounds before falling unconscious and failing death saves. However, one round spent outside the water is enough for a player to “take a breath” and reset their individual timer.
• Clerics must worship deities. Characters who gain their power from “ideals” or “concepts” are Paladins or Druids. If you are having trouble finding a deity that works for you, the DM can help create or re-skin one for you.
• Populations of Faerûn have been greatly increased (particularly in urban areas) to give a more “lived-in” feel. For example, Lyrabar (the capital of Impiltur) has had its population increased from 50,000 to 500,000; it is now more analogous in scope and feel to the city of Lisbon. (Well-established cities like Waterdeep can now expect populations in the millions.)
• To give a sense of value, one gold is roughly equivalent to $100 in real-world value. This means one electrum is equivalent to $50, one silver is $10, one copper is $1, and one shilling (homebrew) is $0.10.
• A living creature has both a “soul” and an “animating spirit.” A creature with an animating spirit but without a soul is a mindless undead. A creature with a soul but without an animating spirit cannot function, and the soul quickly leaves. An animating spirit is sometimes called a “life force” by spells that sap it. (This is based off of the wording in the spell Speak With Dead.)