Sanctuary is introduced as part of the main quest.
It is a pocket realm where the player can engage in the various systems to improve their character in Bards College Expansion, as well as a place to practice Shouts and Chants without having to worry about killing or upsetting other NPCs.
Sanctuary was intentionally designed to NOT be a player home, and instead a place to focus on training. For that reason, items dropped here will be instantly returned to the player's inventory so they can't use it as a storage place.
The player has two options to enter and exit Sanctuary.
The first is by activating the mural in Sledrig's Quarters to enter, or the portal near the Cleansing Pool to exit.
The other, is a new Shout called Sanctum's Resonance - which can be unlocked after completing the quest Sanctuary is a part of if the player finds all of the tablets (see Sanctum's Resonance section of the Shouts page for details).
This Shout will teleport the player to Sanctuary, and if used again, will return them to the exact spot they were at when using the Shout initially. If the player Shouted their way in, activating the portal will also return them to where they used the Shout.
While engaging with Bards College Expansion, the player will occasionally receive a misc item called Bardic Inspiration - these are used as a currency to unlock new perks.
This is given for a variety of activities: playing music, insult dueling, using Shouts, completing quests, reading Skill Books, discovering locations, attending classes (be in a classroom in Bards College and stay there during a lecture), composing Ballads, using skills in dialogue (Bribe, Persuade, Intimidate), Chanting, and learning Words of Power.
Not all activities will give Bardic Inspiration at the same rate, but the overall rate is such that most players engaging in the systems will have enough Bardic Inspiration to fill out the entire Skill Mural by the time they've completed the quests in Bards College Expansion.

The mural centerpiece inside Sanctuary represents a Skill tree for Bardic skills. The star symbols operate the same as those on the default UI's perk tree.
Once the player has at least one rank in a perk, any perks that require it will become available.
Below is a chart of the various perks available.
| Perk | Effect | Pre-requisite | Ranks | Cost(s) |
|---|---|---|---|---|
| Draconic Knowledge | Skills improve 0.25/0.5% faster for each Word of Power known. | N/A | 2 | 1, 7 |
| Spiritual Connection | Stamina and Magicka regenerate 5/10/15% faster when traveling with a follower. | N/A | 3 | 1, 3, 5 |
| Empowered Voice | The power of many shouts is increased 25/50%. This will impact Shouts that can be magnified in some way, such as those that deal damage, have a duration, or increase some stat. Utility Shouts, such as Whirlwind Sprint or Clear Skies won't be affected. | Draconic Knowledge or Spiritual Connection | 2 | 1, 5 |
| Thu'um Mastery | Time between shouts is reduced 10/20/30/40/50%. | Empowered Voice | 5 | 1, 1, 2, 2, 3 |
| Meditative Chant | Doubles/Triples time before the next shout in a Chant must be cast. | Thu'um Mastery | 2 | 1, 3 |
| Chant Mastery | Resource cost of using the Cadence Rod is reduced 10%. | Meditative Chant | 5 | 1, 1, 2, 2, 3 |
| Dragon's Roar | Shouting staggers all enemies around you. | Chant Mastery | 1 | 1 |
| Entertainer | Gold received when playing music for crowds is increased 25/50/75/100%. | Draconic Knowledge or Spiritual Connection | 4 | 1, 1, 2, 2 |
| Triumphant Melodies | Inspiration buffs from music playing are improved 20/40/60/80/100%. | Entertainer | 5 | 1, 1, 2, 2, 3 |
| Diminished Presence | When playing music in combat, you will be less likely to be attacked if your followers are fighting. | Triumphant Melodies | 2 | 1, 3 |
| Battle Bard | While you play music during combat, your followers gain additional Empowered effects. Drum = +25/50/75% Physical Damage Dealt, Lute = +25/50/75% Magic Damage Dealt, Flute = +25/50/75% Damage Resistance | Diminished Presence | 3 | 1, 3, 5 |
| Dragon's Dirge | Once per day, this ability causes playing music to lure a Dragon to attack. | Battle Bard | 1 | 1 |
Players using other mods with features that reduce Shout cooldown should avoid taking too many ranks in Thu'um Mastery. Reducing Shout cooldown by 100% or more can break Shouting!
The table to the right of the Skill Mural will appear decorative at first, but once the player learns Chanting, any time they return to Sanctuary, if there are new Chants the player hasn't yet unlocked whose Shouts match those the player knows - a Codex of that Chant will appear on this table for the player to loot.

A Crystal stand to the left of the center of the space is introduced shortly after the player first enters Sanctuary during the main quest.

Activating it once while the player has an unused Resonance Crystal in their inventory will ask the player if they'd like to place one.
Once a Resonance Crystal is in place, the player can activate it and will be asked if they'd like to Do Nothing, Imbue it with a Dragon Soul, or Take the Crystal.
The first option simply closes the menu, the second spends a Dragon Soul and charges the crystal (if the player has a Dragon Soul avaiable), and the third option returns the Resonance Crystal to the player.
Once a Resonance Crystal is charged with a Dragon Soul, the Crystal can no longer be interacted with, and the player must use a Shout near it. Doing so will shatter the crystal and summon an enemy to fight. Generally this will be the echo of a humanoid character, but for some dragon-related Shouts, it will be the echo of a Dragon instead.
The player must defeat the echo; doing so will spawn the Resonance Crystal with the enhancement name affixed in the ashes of the echo's corpse for the player to loot (Example, Resonance Crystal - Unrelenting Echo).
Just to the right of the center of the space is a large blue crystal embedded in a stand. These crystals will dramatically speed up recovery time of the player's Shout cooldown. This is here to allow the player to more quickly test out their new Resonating Shouts.

These crystals can also be found in dungeons added by Bards College Expansion, generally near a puzzle that requires making use of a Shout.
The Lecturn cannot be used until it is introduced as part of the main quest, but this allows the player to place the tablets and then interact with them to learn new Words of Power. Doing so shatters the tablet.

Near the entrance is a pool of water. Activating this allows the player to place a Resonance Crystal with a Shout trapped inside and reset it so they can capture a new shout within. (See Resonant Crystal Stand above for explanation of trapping shouts)

Sanctuary may appear to have a weather cycle at first glance, but it is actually changing as the main quest progresses. The explanation for this can be found during the main quest.