Dead Cells

The Teleportation Rune will probably be the 2nd or 3rd rune that you unlock, and requires the Vine Rune. It is earned by going from The Prisoner's Quarters (first area) and exiting through to The Toxic Sewers.

As you work your way through The Toxic Sewers, you'll automatically speak to a prisoner that has lost his rune somewhere in the level. Search the entire level until you find him again, near a pit that you can drop down. Once here, you'll have to fight an Elite Slasher. Killing them will drop the Teleportation Rune, automatically equipped as a permanent unlock..
With the Teleportation Rune equipped, you will be able to interact with coffins that will teleport you to new and secret areas. It will allow us to exit The Promenade of the Condemned to Ossuary, which also allows us to see The Forgotten Sepulchre.

This rune is located in the Toxic Sewers, to access this area, you'll need to get the vine rune located in the Promenade of the Condemned and then in the prisoners quarters, you can climb a vine to gain access to the Toxic Sewers. I have described how to do everything in my playlist on YouTube which takes you through each part.

The NPC will put his hands through the grate on arriving at the area, then as you progress, you'll come across an empty grate or a grate with him again telling you that there's danger ahead. This is correct, there is an elite slasher once you drop down. Defeat this slasher and you'll obtain the teleportation rune.

The slasher has a quick triple melee move with the third being a ranged slash and then a short break before their next combo. I would recommend trying to take on this enemy at range.

Heres a video and below is the full playlist of all runes and areas:

Playlist:
https://www.youtube.com/playlist?list=PL2QolhM4SgygXMJl5CQ6Z...