RUNE 020
Inside the safe of Pratchett's house. The code is 473 from the three paintings hinted at in the clue you find on the note in his place.
RUNE 021
On the desk right in front of you when you first enter Midrow Substation.
RUNE 022
In Sokolov's laboratory on the roof.
Lady Boyle's Last Party
RUNE 023
The red Weeper inhabited multi story apartment at the bridgehead. Blinking in to the top-floor balcony puts you right next to the charm and the rune.
RUNE 024
There is a short metal bridge spanning a channel between the Pratchett Warehouse and the Boyle Estate; put the Boyle Estate ahead of you and Pratchett's warehouse behind and to your left. The rune is in the channel of water to your left. Simply follow the stairs to the water level and fetch it.
RUNE 025
In the basement vault of the estate. The basement vault key is in Lydia Boyle's bedroom - the second floor bedroom closest to the stairs with the Wall of Light (her sisters' bedrooms are on the other side of the foyer pide); check the nightstand near the bed for the key. The rune is in the basement (wine cellar) vault, which should be easily accessible from the kitchen.
Return to the Tower (Hounds Pit)
RUNE 026
If you dueled Lord Shaw (remember you can Sleep Dart him in the duel), Pendleton gives you a rune after you speak to him about the Boyle mission.
RUNE 027
In the Hounds Pit. If you did not indiscriminately slaughter the Boyle sisters and spare them, you will get this rune from one of the surviving sisters. It will be in your room. A note at the tavern's entrance (near Wallace) clues you in, and the second note (by the rune) will tell you the identity of your benefactor.
RUNE 028
Speak with Callista in the bar and then try to locate Emily. Dark Vision helps here. One of her possible hiding locations is in Corvo's room, the corridor furthest from the bed. The rune is given to you by Emily.
Return to the Tower
RUNE 029
The bunkhouse on the side of the main entrance has a rune, but its front door is covered by a Watchtower (turret). Deactivate the tower first, and then take your time sneaking in when the Tallboy moves; otherwise, do a re-program and wipe the field clean. The rune is under one of the bunks inside.