This is an alternate way to capture the idea of magic items changing from plane to plane without simply tracing a path to the home plane and reducing the item’s bonus. I always liked the idea of magic items varying away from home, but the implementation was a lot of math for no real benefit to the player.

Each plane (or distinct realm within a plane) has a collection of up to half a dozen keywords. Magic items created in that location tend to acquire the same set of keywords. Additionally, spells have at least one keyword that is salient to the spell’s effect. Some special abilities may have similar resonance to equivalent spells.

Magic items may have special powers that are only active when in a plane/realm with matching keywords, or may just be more generally effective when more of the keywords match. This might be a specific ability mapped to a given keyword, or may be that certain powers are only active when specific keywords are active.

Spells are generally treated as being cast at +1 slot level if they have at least one matching keyword with the local plane/realm (e.g., fireball is always cast as at least a 4th level spell in a Hot realm).

Some spells or other magical effects may temporarily apply a keyword to a local area (e.g., the darkness spell might create the Dark keyword within its area).

Keywords

In addition to the keywords below, each plane is its own keyword name.

Energy

  • Bright (Radiant, Light, Sun)
  • Cold (Cold, Ice, slowing effects, winter)
  • Corrosive (Acid, disintegration)
  • Cutting (Slashing, effects that cause DoT)
  • Dark (Necrotic, Darkness, Night)
  • Energetic (Lightning, energy buffs)
  • Hot (Fire, heating effects, summer)
  • Invisible (Force, Invisibility)
  • Mental (Psychic, Mind-Affecting, Telepathic)
  • Penetrating (Piercing, effects that bypass defenses)
  • Smashing (Bludgeoning, effects that destroy objects)
  • Sonic (Thunder, sound illusions, silence)
  • Toxic (Poison, physical debuffs)

Misc

  • Bestial (Animal effects)
  • Colorful (Color effects, visual illusions)
  • Confining (restrictive/paralyzing effects)
  • Disjointed (teleportation effects)
  • Fluid (Water-related effects)
  • Metallic (Metal conjurations/transmutations)
  • Motive (Imbuing motion to things)
  • Mystic (meta-magical effects like anti-magic, detection, etc.)
  • Prophetic (many divinations)
  • Protective (defensive effects)
  • Restoring (Healing effects, restorations)
  • Stonelike (Stone/earth conjurations/transmutations)
  • Tempestuous (Air and storm-related effects)
  • Transforming (Physical transmutations)
  • Wooden (Wood/plant conjurations/transmutations)

Alignment

  • Chaotic
  • Evil (includes Evil spells like animating dead)
  • Good
  • Lawful

Known Realms

  • Sigil: Outlands, Confining, Cutting, Dark, Disjointed, Metallic

Example Item Resonance

  • Bag of Holding: If all keywords are matched, the bag only weighs 5 pounds. Each keyword not matched increases the weight by 5 pounds (up to 35 pounds in realms that don’t match at all).
  • Folding Boat: If no keywords are matched, this item cannot change from its current configuration. If two or more keywords are matched, it can become a small boat (or return to its collapsed configuration). Only if four or more keywords are matched can it expand into its vessel configuration.
  • Goggles of Night: The goggles grant Darkvision with a range of 30 feet plus 10 feet per matched keyword (e.g., up to 90 feet when six keywords are matched).
  • Immovable Rod: The rod can hold up to 6000 pounds of weight plus 1000 per matched keyword. The Strength check to move it is DC 26, +2 for each matched keyword.
  • Potion of Climbing (and others with a normal 1 hour duration): The potion lasts for 30 minutes, plus 10 minutes for each matched keyword.
  • Potion of Healing (and improved versions): The flat add of basic points of healing is equal to the number of keywords matched (e.g., heals 2d4+3 with three matched). This is multiplied for the improved potions (x2 for greater, x4 for superior, x10 for supreme).
  • Ring of Swimming: You have a swimming speed equal to 30 feet plus 5 feet per matched keyword (e.g., 60 feet with six matched keywords).
  • Weapon +1: This item retains its +1 bonus no matter how many keywords are matched. However, any special abilities may come and go based on the resonance.