Safehold

A safehold was a name used for extradimensional spaces in Faerûn, typically livable ones. Some sages called them "elf holds".

Characteristics
Practically all safeholds were accessible only from one location; some required a certain key as well, usually an item or a spoken word. A few keys could be more arcane and complex.

A safehold somehow weakened the planar fabric, making the location vulnerable to interplanar intrusion; this was said to have been a decisive factor in the damage that Myth Drannor took from the Army of Darkness.

True safeholds were extradimensional spaces; their entrance portal was often opaque and invisible. Safeholds were finite, and typically rather small, about the size of a room with enough room for four people or maybe twelve standing up. Being extradimensional, they kept off most forms of detection. They copied the traits from the plane to which they were adjunct, typically the Prime Material plane.

They had a single continuous wall encircling them, typically covered over with some construction, and some form of illumination. True safeholds always had some manner of refreshing air, through invisible links to the Material Plane.

Construction
Safeholds had been created in profusion by the elves of Faerûn, but they were not created anymore by the 14 century DR. Per the Knights of Myth Drannor, that ruined city had held hundreds of such safeholds in its heyday.

The air circulation of safeholds was made through special spells cast on stones that were then hurled high with slings; the highest point reached by such stones became a small portal for air absorption.

The construction of safeholds seemed to have been greatest during the centuries after the fall of Myth Drannor; the spells for the construction of safeholds had been just about lost by. The construction of safeholds called not just for spells that cloaked and locked the entrance, but also to circulate air and keep the temperature. Some even had means of removing personal waste well away from the location. As it was not common knowledge, a would-be safehold creator needed to devise the process anew; it might have required the insides of transdimensional creatures, or special binding rites, akin to those of a weapon with a legacy. Candlekeep may have held sufficient knowledge to get a creator, had he already surpassed conventional magic, started.

The would-be creator needed first to create the extradimensional space, anchor it to a given location, and then shape it correctly. If they wanted to create portals afterwards or add new features, unique magic items would need to be devised, then linked to the walls. One of them would become the portal for the entrance; other, unknown spells would have to be chosen for the temperature and humidity desired, as well as for links that would furnish it with air, and the ultimate resilience and stability that the space needed.

These spells, known in the days of Myth Drannor, were unknown in. Without them, the space would be swept in a matter of days, twist itself into a cavity full of wild magic, or worse. The spells linking the safehold to external air sources without allowing anything inside were also lost; modern safeholds used smaller portals, which could let in other things as well.

The Sword Heralds created a number of safeholds starting in 620 DR. In particular, they created in 640 DR a labyrinth full of foul beasts, for the amusement of House Auantiver's youth. This was the site of the foundational event for the Men of the Basilisk in 1247 DR; they were looking for more safeholds into the late 14 century DR.

Safehold Collapse
A safehold whose walls were struck with disintegrate, or subject to other magical effects, might expel all of its contents through a portal, with the force of an energy vortex.

Notable Safeholds
A ring once given to Azoun Obarskyr IV transported him to a safehold.

An elven safehold crammed with weapons was said to exist in the Sharburg, within Tegal's Mark, summonable with the right words. The phantom skull in the Elfskull Inn was said to be the marker for the entrance of a safehold belonging to the Sword Heralds. Chessenta and Turmish were said to be riddled with safeholds.

Either Volo or Elminster claimed to know of a safehold accessible in the Dales by leaping off of the Standing Stone at a certain time of day, which led to a labyrinth guarded by a dozen beings resembling liches. Depending on the tales, the labyrinth's center concealed a spell library, a stair to the Underdark, a portal to the Outer Planes, or a Cult of the Dragon cache.

Many mages had attested to a safehold accessible in Myth Drannor from an once magnificent building, which held a number of amenities but was guarded by a death tyrant whose eyes emerged from the walls that attacked anyone who attempted to remove the contents. They also attested to a sensation of being surveilled, perhaps even mentally, while resting there.

The Speculum, in Myth Drannor, was the site of a safehold, accessible by placing a magical key in a hole in the flagstone floor of its central hall. It was believed to have been established by Alaghlar of the Horns.

A hidden safehold in the western, older part of Myth Drannor was known to hold a deepspawn.

A safehold dubbed "The Nighthole" was said to exist in Athkatla, in the use of an unscrupulous, secret merchant society, and to be accessed only at night.

Both Castle Waterdeep and Piergeiron's Palace were rumored to have such safeholds, and Suzail's Palace of the Purple Dragon was known to have at least one. The latter was rumored to be festooned with the bones of would-be usurpers.

The Deep Imaskari who didn't flee into the Plains of Purple Dust after their defeat to the Mulhorandi led by Nezram were said to have fled to extraplanar safeholds.

Brymmyn Thorl had created unique safeholds, accessible from existing portals with a separate key. He added such safeholds to many a gate.

Aralagath Tarsil had discovered a safehold accessible from anywhere in Faerûn, the key to which involved a word, a gesture, and water or stone in the palm of his hand.

The mage Perendra of Voonlar had a safehold on the path to her root cellar, attached to a portal; the words "Orntharm Felderenslor" altered the portal's destination to be a safehold of hers. Anyone casting a spell there was ejected from the space.

Elves had built safeholds into the walls of Belkram's Fall in Undermountain.

The Brotherhood of the Secret Quill had a mammooth vault known as the Vault of the Bound, for storing copies of their most important texts; this vault was also known as a safehold.

The Knights of the Shield met in safeholds regularly.

The Tel'Teukiira had their base of operations in the Silver Safehold of the old Sword Heralds of Cormyr. The place was accessible through a Teukiir badge. Khelben Arunsun built the Silver Safehold around. It was connected to Blackstaff Tower by a gate in the cellars.

Priests of Mystryl were expected to keep magic safe into the future; amongst other locations, they were known to cache it in safeholds too.

Castle Cormanthor had enough safeholds that, with their full use, it could stand to hold up to eight thousand people.

The Cowled Wizards kept 16 safeholds across Amn. Emperor Shoon had a number of safeholds.

Trivia
Elminster's evasion, when used by Elminster, took him to an undisclosed location which he called "Safehold". That location wasn't really a safehold, but a satellite orbitting H'Catha. Per some of the most obscure sages, it had been a gift from Azuth, after the original owner for whatever reason went missing. Other sages included the fact it had only been ever visited by Ao.

Some people spoke of "safeholds" where to hide money with no one knowing. Such a safehold could refer to a location or a service.