The Gatecrasher's Silver Key: A Wondrous Item for 5e

The Gatecrasher’s Silver Key

Wondrous item, very rare

The head of this oddly angled, oversized silver key is set with a blazing red gemstone and etched in extraplanar runes. This gem glows faintly when within one mile of a portal to another plane of existence, including portals to demiplanes and extradimensional spaces such as those created by a magnificent mansion spell. The closer the key is to the portal the brighter the gem glows. By taking advantage of this effect one can search for the portal’s exact location. Using the key to search for a portal takes one hour and a Wisdom (investigation) check with a DC of 9 + the spell level of the effect that created the portal. If the portal was not created by a spell the DC is 15. Success guides you to the portal’s location. Closed or invisible portals remain closed or invisible, though you are aware of their precise location. Failure means a wasted hour of wandering, but you can try again.

The gatecrasher’s silver key can also force open closed portals. Forcing open a portal requires an action and an Intelligence (arcana or religion) skill check with a DC of 12 + the spell level of the effect that created the portal. If the portal was not created by a spell the DC is 18. If you spend a full minute using the key to “pick the cosmic lock” you have advantage on this check. If the check fails the power of the key fades and it cannot be used again until the next sunrise.