Operations as defined by the Annulus ruleset includes anything that adventurers do to manipulate, analyze, investigate or reform mechanisms, objects, structures or scenes to achieve a desired result. This includes but isn't necessarily limited to activities such as:

• Picking a lock.
• Hacking into a database.
• Disabling a mechanical trap.
• Picking up the trail of a fugitive.
• Forging official documents.
• Sabotaging a wagon wheel.
• Jamming a door shut.
• Hotwiring a motorcycle.
• Fixing an engine.
• Checking a crime scene for clues.
• Drawing a magic circle.
• Building a raft from driftwood and junk.
• Unclogging a toilet.
• Performing surgery.
• Escaping from confinement.
• Removing a key from around the neck of a sleeping ogre.
• Making a decent copy of the writings in a ruin.
• Reforging a sword of legend.

All operation activities use the same method to resolve success or failure and are known as Operation Challenges.

There are four broad categories of op challenge, as such:

• Crafting challenges involve making physical things such as building a wall, forging a sword, drawing a magic circle, or repairing an engine.
• Investigation challenges involve analyzing an area, creature or object to reveal hidden information such as scoping out a crime scene, tracking prey through the wilderness, finding the location of a hidden safe or deducing information about a subject based on their appearance.
• Knowledge challenges involve the application or deciphering of complex, obscure, poorly-conveyed or advanced information such as breaking a code, performing ritual magic, auditing a business or correctly reading a faded treasure map.
• Finesse challenges involve exploiting or bypassing the safeguards of others such as opening locks, shutting down security systems, sabotaging mechanisms, or picking pockets.

When setting up a given challenge, the GM will announce what sort it is. A challenge can be of two different types simultaneously if they both fit- for example, bypassing a magical warding spell might be of both the Knowledge and Finesse types simultaneously.

A challenge's type is important for determining which adventurers are best suited for it. By default, all checks made in every challenge are made with three dice. Training perks can increase the number of dice rolled, but only for certain challenge types.

There are four different difficulties of operation challenge: easy, medium, hard, and impossible. The difficulty of a challenge determines the number of successes required to be effective with all checks applied to the challenge. Easy challenges require two successes, medium challenges require three, hard challenges require four and impossible challenges require five. The GM announces the difficulty of a given challenge when setting it up.

To set up an operation challenge, the GM rolls six of 12-sided dice and places them in a line in the order they were rolled. For example, if the GM rolled a 7, 9, 7, 3, 11, and 5 they would line them up like this (assuming no dice start hidden, see Hidden Dice below for an explanation):

[7][9][7][3][11][5]

The goal of an operation challenge is to make it so every die in the challenge is exactly one number different from every die it neighbors. For example, a sequence of [1][2][3] is a valid solution, as is [3][2][1] and [1][2][1]. If for some reason an operation challenge has only one die, then it is automatically considered solved no matter what number is displayed on said die.

Sometimes not all the parts of an operation are immediately apparent. When the GM rolls the six 12-sided dice for a challenge, they first secretly roll six six-sided dice in a line in the order that they are rolled where none of the players can see. These six-sided dice correspond to the player-visible twelve-sided dice. Any of the six-sided dice that display a result of 1, however, are considered “hidden”. The GM does not roll a corresponding 12-sided die for any of their six-sided dice that display a 1.

For example, say the GM secretly rolls their six-sided dice and get the following results:

[5][3][4][3][1][2]

The presence of a 1 means that one of the dice in the challenge is hidden, so the GM rolls five 12-sided dice in plain view of the players. The players solve the current challenge as-is, but then upon “solving” the puzzle, the hidden die is revealed and inserted into the die chain in the appropriate location. If there are multiple hidden dice, only one is revealed at a time and only when all visible dice are “solved”. The GM can reveal multiple hidden dice in any order they please.

In the above example of [7][9][7], the three numbers are not a valid sequence since the [9] is 2 points different from both of the [7]s beside it. Fortunately, any adventurer can use a minor action to attempt to change one of the dice to a number 1 higher or lower.

A creature could therefore change the above example into this:

[7][8][7]

with just one action, making that part of the sequence already “solved” and allowing them to turn their attention to the rest of it. Adjustments are not guaranteed to succeed, however- sometimes they result in a jam instead of the desired number change (see below).

Every time a creature makes an adjustment on any die in an operation chain, they must first roll an op check to see if they screwed something up or otherwise made things more difficult for themselves. This is a four-die check that requires a number of successes dependent on the difficulty of the challenge. If the check fails, the die jams and its number is not changed.

When a die “jams” it becomes stuck on whatever number it currently displays. It is suggested that the die be marked in some way to visually represent its jammed status- one simple way is to simply turn it so that the number it displays is upside-down in comparison to the other dice, or physically move it slightly out of the line that the others are in.

A jammed die cannot be manipulated any further in any way. If dice are jammed in such a way that solving the operation challenge is impossible (such as by having two adjacent dice with numbers more than 1 point apart both jam) then the operation challenge fails.

Adventurers all have access to a limited number of Toolkit abilities that can be used to make overcoming operation challenges easier. See the Toolkit page for more details. More difficult challenges will almost necessitate the use of a toolkit.

Toolkit abilities require a check to use. If a toolkit ability is attempted but the check fails, then that ability becomes unavailable for use for the remainder of the challenge but the challenge is otherwise unaffected by the check's failure.