Cipher Coins are green coins found throughout Plague of Shadows. Similar to music sheets, once a coin is collected, a transparent grayscale version of it will mark where it once was. Collecting a gray coin will not increase the player's coin amount. There are in total 420 Cipher Coins throughout the campaign.
A Cipher Coin can also be found embedded in a wall in each stage of the Order of No Quarter members with the exception of Pridemoor Keep. They indicate hidden areas where Plague Knight can obtain Relics (or trade with Chester in the Iron Whale).
The numbers of Cipher Coins in each stage vary by type:
- 30 - Plains, Order of No Quarter Stages, Tower of Fate Entrance & Ascent
- 20 - Arcana Courses and Hall of Champions
- 6 - Armor Outpost
- 4 - Village
Cipher Coins can be spent with Mona or Percy in the Potionarium on research. Each research unlocks more options for Plague Knight's bombs to be bought in gold. The catapult in the Armor Outpost also requires Cipher Coins for Percy to fix it.
- 40 - Research 1. Unlocks Float Casing, Component Powder, Quick Fuse, Sentry Fuse and the Bullet Burst
- 60 - Research 2. Unlocks Orbit Casing, Cluster Powder, Remote Fuse and the Frost Burst
- 80 - Research 3. Unlocks Drop Casing, Whirl Casing, Sparkler Powder, Impact Fuse and the Spin Burst
- 50 - Fixes the Armor Outpost Catapult
If all 420 Cipher Coins are collected and taken to Percy at the Potionarium, Plague Knight can obtain the Pandemonium Chalice. Obtaining the Pandemonium Chalice will also fix the catapult if this has not already been done. The Pandemonium Chalice can be shown to the Troupple King to receive the Pandemonium Cloak.