Wizard's Tower

Small towers dotted about Highpass, created by magic

Set up by wizards, usually high elves travelling far from their home, wizard's towers can occasionally be found in secluded spots close to a settlement. 
In Highpass, wizards are rare and magic is considered very dangerous: there is no college or school for learning magic, only lost spellbooks finding their way to those thirsty for knowledge. Most fledgling wizards must forge their own path and experiment with magic alone, but a lucky few come across wizard's towers, where they can learn from generations of arcanists past.
Some wizards remain in a tower for a hundred years or so, learning all they can in the area, before setting up another base of operations elsewhere. The remaining tower is then equipped with a teleportation circle, becoming a network and means of transportation for its master in addition to a place of knowledge and learning.
Occasionally a wizard will either forget to maintain a tower in the network or fall foul of the dangers of the profession and vanish. Some of the latent magic left in these abandoned towers becomes wild, creating magical hazards or monsters that haunt the local area. Adventurers will occasionally be hired by the nearest town to break in and solve the problem, and be rewarded with magical treasures or spellbooks.
Game Note: A wizard's tower sometimes contains new spells, such as the following spell found in a tower once belonging to Dr. Miles Grimtooth.

Grimtooth's Almanac of Abjuration

Grimtooth's Web of Warding

2-level Abjuration

Casting Time: 1 action

Range/Area: 20ft radius

Components: V, S, M

Materials: One strand of silk

Duration: Concentration, 1 minute

A complex web of arcane energy stretches out in a 20ft radius from the caster, who cannot move without ending concentration on the spell.
The web has 20 hit points. Creatures of your choice within the spell's radius use the web as a shared pool of temporary hit points. Once the web's hit points are reduced to 0, the spell ends.
If an area of effect like a Fireball spell would damage multiple creatures within the web, the damage is reduced by the web's current hit points before being applied to the creatures.

At higher levels: The web gains an additional 5 hit points for each spell level beyond 2nd.

Available for: Wizard, Sorcerer, Bard