Portals manifest as panels of colourful light, each between the size of a small car and the size of a truck (though it is likely that portals can open to larger sizes than this, as monsters too large to fit through portals these sizes have been seen in the Human Realm). When a portal closes, the panel of light will shrink away.
Humans, monsters and objects can pass through portals by simply stepping or being carried into a portal and almost instantly emerging out the other side. It was also shown in Through the Looking Glass that pulse/energy blasts can pass through portals as well as matter.
Apparently, portals lead across space as well as dimensions, as in Through the Looking Glass, two portals were only miles apart in the Monster World, but in the Human World, one was in Lakewood while the other was in Hawaii. Also, some portals, shortly after opening, will suck everything nearby in and onto the other side until they close, but others won't.
Dimension Mites can eat open portals. It would appear that the amount of time it takes for a portal opened by Dimension Mites to close corresponds to the number of Mites which opened it.
A portal will usually only stay open for a minute at the most before it closes, though under several circumstances, portals can stay open for much longer:
- If a Dragon crosses through to the Human Realm, the portal it came through will stay open until it returns through.
- Kaiju feeding portals - portals that Kaiju come through to be fed humans by Mind Leeches - appear to stay open until either the Kaiju return through, or the Mind Leech is destroyed.
- Due to Troop Grid's unique frequency, if a portable Troop Grid is lost into the Monster Dimension, it will cause a portal to open. This portal will only close when the Troop Grid is either destroyed or returned to the Human World.
AppearancesEditDimension Mites, opens a portal which she, Jake and Felix return several captive monsters through to the Monster World. The portal presumably closed shortly after.
Soon after, Gus uses the same Dimension Mites to open another portal in Jake's room which a Quadro-Gob comes through. The portal then apparently closes. A short time later, Hayley uses the Dimension Mites to open another portal in the place of the previous one, which both the Huggie Bear and the Quadro-Gob are forced through back into the Monster World. The portal then closes.
Felix uses a canister of Dimension Mites to open a portal in Troop HQ, which an Eris Fairie crosses through back to the Monster Dimension. The portal then closes.
A portal opened in the woods near or in Lakewood, and allowed through a baby Dragon, and later the mother Dragon. As a result of the Dragons' presence in the Human World, the portal remains open until the two Dragons return through to the Monster World. The portal then begins to suck Phoebe through into the Monster Dimension, but she is pulled away from the portal before it can suck her in. The portal presumably closes shortly after.
A swarm of escaped Dimension Mites open a portal in Troop HQ, which Fraido incompetently walks through in amazement. The portal then begins to suck everything nearby in, including Gus who allows it to do so. The portal closes shortly after Gus's Monster Magnet is deactivated.
A portal opens in an alleyway for the Kaiju feeding program and allows three Kaiju through. The portal closes when the two surviving Kaiju flee back through into the Monster World.
Later, another portal opens at a video game convention and allows the same two Kaiju through. However, they flee back through to the Monster Dimension once again, causing the portal to then close.
Some time later, another portal opens in the same alleyway as the first and allows the two Kaiju through. Decklyn Patrick, possessed by a Mind Leech, emerges through the portal back into the Human World. The portal presumably closes shortly after.
A swarm of escaped Dimension Mites open a portal in Troop HQ which begins to suck in Cadence. The portal closes moments after Cadence, with Jake's portable Troop Grid, is sucked through into the Monster World.
A portal opens, connecting a park in the Human World and an underground cavern in the Monster World, and a pair of Basilisks come through. Due to the presence of Jake's portable Troop Grid in the Monster World, the portal remains open.
When Jake, Hayley and Etienne locate the portal, Jake travels through to the Monster Dimension, while Hayley and Etienne put a tent around the portal to hide it. Over the course of an hour, at least three monsters try to cross through the portal to the Human Dimension, but are stopped by Hayley. After about an hour, with Jake's portable Troop Grid destroyed, the portal closes, but not before Hayley jumps through into the Monster World.
Shortly after the portal closes, Troops across the globe each open a new portal via Dimension Mites for Jake and Hayley to find and cross through back to the Human World. Jake, Hayley and Cadence escape through a portal (connecting a desert in the Monster Dimension to the Hawaii Troop HQ in the Human Realm) back to the Human World. All of the portals then close.
A portal opens in Troop HQ (it was presumably opened by Kirby via Dimension Mites), and Kirby allows the captive Sniffer to return through to the Monster World. However, it turns out that even the monsters in the Other World don't want the Sniffer there, so the Sniffer comes back through the portal. Kirby tries to push the Sniffer back into the portal over and over, only for him to come back through each time, until eventually the portal closes with the Sniffer still in the Human World.
A Troop disposal team use a portal in a rural forest to return captive monsters though to the Monster World, including a Gleegor and an Evolvosaurus. The portal closes shortly after the Evolvosaurus crosses through.