Xavier Remington 
You’ve had a delightful day and an enchanting evening as the Midnight Witching Hour approaches. You begin smelling sulfur as intermittent high pitched sounds subtly echo through your house. Every so often the lights flicker as thing begin to heat up even as you jack up the air conditioning. The basement seems to be the source. However, you just assume you’re imagining things even as you see a blurry circle or sphere forming before you. This can be in the middle of the room, in the floor, ceiling, or wall. You rub your eyes and decide you simply need some sleep. As you sleep that sphere begins glowing orange with fire as a horrifying mirage of Hell appears!
You awaken during the 3 AM Devil’s Hour in a cold sweat to shrill screams of sheer terror amid calamitous cackling. The thermostat indicates your home is pushing 100 degrees Fahrenheit for no logical reason! You peer down the basement steps to witness an eerie orange glow. You cautiously descend into the horrid smelling basement bellowing with crackling flames, the sounds of suffering, and the deep gleefully laughter of evil. Before you is a window into Hell itself or in some cases the Underworld. Sometimes merely a parallel dimension. If you step close enough you will find out it’s a doorway to a place that nightmares are made of!
Whatever can you do? Why is this living hell even happening? There are many reasons why a portal to Hell would appear in your home. These include Curses, your home is the site of a demonic ritual, a prelude to you or another being possessed by a demon, your home lies on a dark metaphysical energy center, a previously cloaked entrance to the Underworld, or even a random a paranormal anomaly. These are just to name a few! Thankfully, most of the time the demons or dark gods beyond the alarming entrance have no idea it’s there unless they accidentally happen upon it or are in contact with magical practitioners who conjured it. Just stay at least a good six feet away as it may have a powerful gravity-like pull to suck you in!
These things take some hours to form. If you can catch it in time then it can be prevented. Douse the area with holy red sea salt, holy water, and blessed oils while reading verses from the Bible. Getting a Priest to perform an exorcism ritual should work for a rapidly forming Hell portal. If the paranormal portal is already there you can still do all the above while creating a thick holy salt line on the floor around it to prevent anything from coming through. Placing several opened Bible’s or other religious books around it can help as well. Constant prayer may be your only hope when facing this horror! Simply placing a black curtain around it will prevent dark spirits from seeing that it goes to Earth.
In order to close this insane opening, you’ll need a parade of Priests, witches or other magicians. Preferably witches practicing Enochian Angel Magic. They will call upon Angels to close the abomination as they paint Enochian sigils all over your basement in holy blood! This may bring attention to the portal on the Hell side causing demons to roar forth! Ultimately we have faith in the power of Angels and they will be driven back. The portal will be extinguished! Afterward, paranormal professionals may recommend filling in the basement with blessed cement or even burning the house to the ground in a blaze of holy fire!
If you choose to abandon the house once a Hell portal forms please contact some manner of supernatural savior as it will continue to grow and possibly be an invasion point for Armageddon! If you don’t know who to call then try the US Paranormal Defense Agency (PDA). You can do this by calling 911 with the first words out of your mouth being “PDA”. Then immediately tell the operator what your metaphysical issues is. They will naturally think you’re nuts and plausibly contact mental health services. However, The US PDA through the NSA monitors all communications with an amazing artificially intelligence supercomputer. PDA Agents will be instantly alerted. This will include scrubbing all evidence of your call taking place. Police, mental health services, and any other non-paranormal authorities will be canceled.
More than likely they won’t be able to end the portal but will contain it. Your home and possibly the surrounding acres will become an official top secret base like Area 51. You and other property owners will be paid a pretty penny to move away and never speak of what happened ever again! We suggest you obey the wishes of these Men In Black or you may disappear!
. . . do inter-dimensional portholes warn if someone has stumbled across them and they are actually in the wrong place at the wrong time? . . . or do the portholes take on the character of the individual who has stumbled across them . . . perhaps presenting itself as a mirror of emotions or thoughts . . . . are they sort of intense life opportunities for transition or growth . . . . what happens when they are ignored? . . .
Naturally occurring inter-dimensional portholes don’t have an intelligence, and so they wouldn’t warn anyone of anything. It a person stumbles through, particularly into a near identical parallel Universe, then they might have no clue what happened.