Spoiler

(You can get these by placing potions of water on the altar of your alignment White=Lawful or L, Grey=Neutral and Black=Caotic or C) p.s Potions of holy water can bless non-cursed items

Spoiler

You can teleport 1 of 4 ways.
.Zap a wand of Teleportation by using the "z" key
.Read a Spellbook of Teleportation than cast it using the "Esc" key
.Step on a Teleportation trap the press C-t which activates the trap on your current position
.Read a random Spellbook with a low Literacy skill level so it Teleports you(Reason unknown)

Spoiler
The Library is located in the Rift.
*grabs stuff from the ADOM GB*

The Rift is a wilderness location found in the northwestern mountains, southeast of the dungeon containing the Tomb of the High Kings. The PC must meet several requirements in order to enter it. A climbing set is required (although ADOM 1.0.0 and g16p2, at least, have a bug which causes this to be ignored) and the Climbing skill must be at 100. The PC must be at least experience level 18. If the experience level requirement is not met, the game responds with: "You do not feel experienced enough for this daunting task." Willpower must be at least 20 OR Perception must be less than six.
If all these requirements are met, the PC will still most likely fall on the way down the Rift, destroying some equipment in the process. Falling can be avoided by having the extremely thin and nimble AND the very light corruptions. This needs further testing. It may be that only the very light corruption is required, as per the fortune cookie message "Being light as a feather makes you very rifty." Alternatively, it may be that only hurthlings can avoid falling with only one of these corruptions, similar to the entrance requirements for the Quickling Tree. There are reportedly 27 luck checks on the way down, whatever that actually means. Being burdened or strained is probably not a good idea. A level 50 PC, not cursed or doomed, with intrinsic Lucky and Fate Smiles, wearing the ankh and the Ring of the Master Cat, unburdened, but without the requisite corruptions, still fell. It is not possible to bring artifacts only into the Rift, since a climbing set (and probably food, although enough *might* be found) is required. Therefore, it is a good idea to store the PC's extremely valuable items, such as scrolls of chaos resistance, in a safe place before entering the Rift. It is also a good idea to bring every bit of junk, such as missiles that do not stack, low quality armor and weapons, scrolls of ill fate, cure blindness and the like, low quality amulets, etc. along. These items are fodder for the RNG, which hopefully will destroy them rather than valuable equipment. Do not be too conservative and leave *all* good equipment behind, because the monsters in the Rift dungeon and especially the Sinister Library of Niltrias can be *very* nasty. Hopefully by this point, the PC has some decent artifact armor and weapons. A corollary is not to rush into the Rift too soon.

It is not necessary to visit the Rift dungeon or the Sinister Library of Niltrias to complete the game, and many who play non-spellcasters completely ignore it.

The whole point of entering the Rift is to gain access to the Sinister Library of Niltrias.

Wizards who visit the Library will find every spellbook available in the game, including Wish. Necromancers, for instance, will not. Necromancers find scrolls in the two large rooms and spellbooks in the small northeast room and the hidden passageway. The exact details of what class finds Spellbooks vs scrolls is being investigated. Spellbooks can be destroyed while in the Library (by blue dragons, for example), so be careful with rare spellbooks.

Equipment may be destroyed while in the Library, so it is prudent to leave the climbing set where it is until the PC is finished with the rest of the Library. There will be monster guardians found on top of every spellbook or scroll. These monsters can be anything and are uniformly dangerous. On a recent trip through the Library, a master lich, ancient dragons, a quickling lord, a frost giant jarl, a stone giant lord, a moloch and a mimic hivemind were found among others. It is wise to bring dragon slaying ammo in case an ancient karmic dragon is generated. Likewise, demon slaying ammo or phase daggers are very nice to have in case a (greater) moloch is generated.