Abjuration · Warded thresholds · Planar security
At the last watch before dawn, a bell rings where no bell hangs. Someone has crossed the gate between worlds. No guard has seen a face, and nothing has been stopped; the ward has given them only the knowledge that the frontier is no longer secure.
At a Glance
| Spell | Portal Alarm |
|---|---|
| Published source | Manual of the Planes; revised for Spell Compendium |
| Legacy spell level | Bard 2, Sorcerer/Wizard 2 |
| School | Abjuration |
| Target | One interplanar gate or portal |
| Duration | 2 hours per caster level, dismissible |
| Trigger | Creature of Tiny size or larger passing through; password may exempt a traveller |
| Warning | Audible or mental, chosen at casting; no identification of the traveller |
| Advanced ward | Improved Portal Alarm provides an image of the traveller and a longer duration |
The Bell Between Worlds
Portal Alarm watches a crossing, not a whole district or the entire contents of a fortress. It is designed to tell a gatekeeper that something substantial has passed through a specific interplanar passage. Its warning may be private, awakening the caster from ordinary sleep, or audible enough to bring sentries running from the surrounding rooms.
It does not close the gateway, prevent enemies from moving, identify a disguise or show the direction of travel. Passwords allow legitimate merchants and messengers to pass without a warning, though an enemy who learns the password can exploit the same courtesy. The location of the gate matters: the mental alarm works only within one mile and on the same plane as the gate, while its audible signal reaches nearby listeners on both sides of the opening.
What Is Happening Right Now?
A caravan arrives at a border gate after the guards have lowered the night barricade. The master merchant knows the password, but her driver has been replaced. As each traveller passes through, the watchman listens for the warning only he can hear. He must decide whether to stop the caravan or let the next realm deal with the intruder.
Spell Rules by Edition
Portal Alarm — D&D 2024
No official 2024 spell named Portal Alarm.
Published local-ward alternative: Alarm, Level 1 Abjuration
Casting Time: 1 minute or Ritual
Range: 30 feet
Area: One door, window or space no larger than a 20-foot Cube
Components: V, S, M (bell and silver wire)
Duration: 8 hours
The caster can specify exempt creatures and select an audible or mental alarm. The audible signal is heard within 60 feet of the ward and lasts ten seconds. The mental warning alerts the caster if they remain within one mile. The spell alerts when an applicable creature enters or touches the warded area.
Example: A gatekeeper wards the floor leading to an interplanar arch. A traveller walking onto that floor triggers Alarm, but the spell does not have a special rule for crossing between planes, nor does it identify the traveller.
This is an edition-legal alternative to protect a local area, not the legacy second-level interplanar spell.
Portal Alarm — D&D 2014
No official 2014 spell named Portal Alarm.
Published local-ward alternative: Alarm, 1st-level Abjuration (Ritual)
Casting Time: 1 minute
Range: 30 feet
Area: A door, window or space no larger than a 20-foot cube
Components: V, S, M (tiny bell and fine silver wire)
Duration: 8 hours
A Tiny or larger creature entering or touching the warded area triggers an audible or mental alarm unless specifically exempted. The mental warning reaches the caster up to one mile away; the audible handbell sounds for ten seconds and is audible within 60 feet. The caster chooses the form of notice when casting.
Example: The alarm rings when a courier enters the antechamber, but provides no proof that anyone travelled through the portal itself. The 2014 spell cannot supply the legacy portal password or cross-planar warning mechanics simply by using a higher spell slot.
Portal Alarm — Pathfinder 1e
GM-approved conversion of a published legacy D&D spell; not an official Paizo spell.
School: Abjuration
Suggested level: Bard 2, Sorcerer/Wizard 2
Casting Time: 1 standard action
Components: V, S, M (a tiny bell)
Range: Close (25 ft. + 5 ft./2 caster levels)
Target: One interplanar gate or portal
Duration: 2 hours/caster level (D)
Saving Throw: None
Spell Resistance: No
Ward a single portal. When a Tiny or larger creature goes through, the caster receives the chosen audible or mental notice unless that creature spoke the password. The mental alarm reaches only the caster within one mile of the gateway and on the same plane. The audible alarm rings for one round, heard clearly to about 60 feet and faintly to 180 feet.
The audible alarm is silenced if the portal lies within Silence; a mental warning is not. Astral and ethereal travellers passing through the gate trigger the ward. A password designated at casting exempts a traveller who says it before passage.
Example: A level-10 gatewarden watches one planar arch for twenty hours. The ward detects an unseen creature’s crossing but cannot tell the caster whether the creature was friend or foe.
Portal Alarm — D&D 3.5e
Published supplemental D&D spell, Spell Compendium, p. 160.
School: Abjuration
Level: Bard 2; Sorcerer/Wizard 2
Casting Time: 1 standard action
Components: V, S, M (a tiny bell)
Range: Close (25 ft. + 5 ft./2 levels)
Target: One interplanar gate or portal
Duration: 2 hours/level (D)
Saving Throw: None
Spell Resistance: No
A Tiny or larger creature passing through the specific gate triggers the ward unless it spoke the password designated when the spell was cast. The caster chooses mental OR audible notification, not both. A mental warning is received only within one mile and on the same plane, without interrupting spellcasting or normal concentration.
An audible alarm sounds like a handbell or buzzer, heard clearly to 60 feet and faintly up to 180 feet, ringing for one round and reaching through closed doors and onto other planes. Magical Silence around the portal suppresses the sound. Astral and ethereal travellers also trigger the ward if they cross the gate.
Example: A ninth-level bard wards a trade gate for eighteen hours. When an intruder crosses without the password, the bard receives the private warning from a nearby tower. The spell provides no mental image or direction of passage. For those features, use Improved Portal Alarm.
Adventure Hooks
The Bell Without a Face
A planar gate rings every midnight, but no one can identify the traveller. The adventurers have to wait at the threshold, cross into the other realm or question whoever taught the guard the password.
The Silence at the Threshold
A rival places Silence on a gate to defeat its audible ward. The watchman must choose whether to renew the spell with a mental warning or summon allies to watch in person.
The Price of the Password
A merchant guild sells safe passage through the gate. Someone has obtained the password and is sending smugglers across without raising the ward.
Related Magic
Improved Portal Alarm adds a mental picture of travellers, their direction of travel, a delegated recipient and an eight-hour-per-level duration. The original second-level Portal Alarm offers none of those additions. Planar Campaigns develops guarded passages between worlds, while Magic Mouth and Hold Portal protect other kinds of thresholds.
Sources and Attribution
The original spell appears in Manual of the Planes (D&D 3.0), then in Spell Compendium (D&D 3.5e), page 160. Reference: D&D 3.5e Portal Alarm. This supplemental book material is not claimed to be Open Game Content, and its mechanics are summarised in newly written explanatory language. The 2024 and 2014 panels use the separate published Alarm spell as a comparison; the Pathfinder entry is an explicitly optional GM adaptation. Original setting scenes and examples written for this entry.
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