An insistent buzzing, a deafening whine – that can only mean the Duke of Flies is near! Can you overcome the Duke and the vast swarms of flies that surround him, each willing to give its life to defend its master? Kill them, tempt them away, do what you must: there can only be one true Lord of the Flies, and the Duke doesn’t take too kindly to competition…
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Setup
Game Modes
FAQ
Challenge Cards
Credits
Setup
Card(s) Needed
Goal
The challenge is won when Swarming The Duke of Flies dies.
Setup
- Choose a difficulty level for the challenge:
Normal
Hard
Ultra Hard - Set up as normal for solitaire/co-op mode.
- Place Swarming The Duke of Flies face up to one side of the monster slots in a final boss slot.
(feel free to use your regular The Duke of Flies card as a stand-in to represent this!) - [ and only]
Set aside the monster cards Fly, Ring of Flies, and Swarm of Flies. These cards start outside the game.
Global Modifiers
A New Master 
Discard a loot card: Roll-If the result plus the number of souls controlled by all players is more than 6, remove a fly counter from Swarming The Duke of Flies and put a fly counter on your character.
A New Master 
Discard a loot card: Roll-If the result plus the number of souls controlled by all players is more than 7, remove a fly counter from Swarming The Duke of Flies and put a fly counter on your character.
A New Master Discard a loot card: Roll-If the result plus the number of souls controlled by all players is more than 7, remove a fly counter from Swarming The Duke of Flies and put a fly counter on your character. Otherwise, remove a fly counter from your character and put a fly counter on Swarming The Duke of Flies.
The Swarm Protects
If a player would take damage, they may remove any number of fly counters from their character and prevent damage equal to the number of fly counters removed in this way.
New Keywords
For this challenge, there is one newkeyword.When a card or ability uses this term, it is as ifthe below was written out in full:
| Fly Swarm: | Random card with “Fly” or “Flies” in its name outside the game. |
Reminder
Remember that the specific rules and global modifiers for this challenge are used in addition to the general challenge rules that apply to all challenges. The general challenge rules can be downloaded separately from maestromedia.com.
Game Modes
Normal 
Swarming The Duke of Flies starts with 18 fly counters.
While there are more fly counters on Swarming The Duke of Flies than the total number of fly counters on all players, attacks can’t be declared on Swarming The Duke of Flies and it can’t take damage.
Each time a monster would take damage, the active player rolls-
1: Prevent that damage and remove a fly counter from Swarming The Duke of Flies.
At the end of each turn, put 1 fly counter on Swarming The Duke of Flies.
Hard 
Swarming The Duke of Fliesstarts with 14 fly counters.
While there are more fly counters on Swarming The Duke of Flies than the total number of fly counters on all players, attacks can’t be declared on Swarming The Duke of Flies and it can’t take damage.
Each time a monster would take damage, the active player rolls-
1: Prevent that damage and remove a fly counter from Swarming The Duke of Flies.
At the start of each turn, put a Fly Swarm in a minion slot.
At the end of each round, put fly counters on Swarming The Duke of Flies equal to the number of 
of each minion, then remove each minion from the game.
Ultra Hard 
Swarming The Duke of Fliesstarts with 18 fly counters.
While there are more fly counters on Swarming The Duke of Flies than the total number of fly counters on all players, attacks can’t be declared on Swarming The Duke of Flies and it can’t take damage.
Each time a monster would take damage, the active player rolls-
1: Cancel the attack and put a Fly Swarm in a minion slot, then make an additional attack on that minion.
2: Roll again.
Each time a minion dies, remove a fly counter from Swarming The Duke of Flies and you may make an additional attack this turn.
At the end of each turn, put fly counters on Swarming The Duke of Flies equal to the number of of each minion, then remove each minion from the game.
Competitive Variant 
This challenge is primarily designed for solo and co-op mode, but you can also play a game of regular competitive Four Souls with an added twist.
Setup as normal for a competitive game. Place Swarming The Duke of Flies face up to one side of the monster slots in a final boss slot (use the competitive variant version of Swarming The Duke of Flies 
).
Players start a game of the competitive variant of this challenge with 12 swarm counters on their character. While there are more swarm counters on the active player’s character than fly counters, Swarming The Duke of Flies can’t be attacked or take damage. At the start of each turn, the active player puts a swarm counter on their character. Each time a monster would take damage, the active player rolls. If they roll a 1, that damage is prevented, and they remove a swarm counter from their character.
The active player can, whenever they have priority, discard a loot card to roll a dice. If the result of the roll plus the number of souls they control is more than 4, they remove a swarm counter from their character and put a fly counter on it.
While players have fly counters, they can choose to use them to prevent damage, if they wish. If they would take damage, they can remove any number of fly counters from their character and prevent damage equal to the number of fly counters removed in this way.
FAQ
What happens if, after using fly counters to prevent damage during an attack against the Duke, there are less fly counters on all the characters than there are on the Duke?
Unfortunately for you, your swarm is no longer impressive enough for the Duke – the attack won’t end immediately, but you will no longer be able to deal damage to the Duke whilst it remains the case that he has more fly counters than you do. Since you can’t escape the attack it is likely he will then kill you!
Can you attack the Duke whilst there are the same number of counters on all players as there are on the Duke?
Yes, as it is only when the Duke has more counters than there are counters on all players that it can’t be attacked or take damage. Watch out, though – if you lose any fly counters during the attack you might get trapped in a fight you can’t win! (see above).
Challenge Cards
Credits
| Creator of Four Souls | Edmund McMillen |
| Challenge Design | Charlie Gill |
| Challenge Art | orisghost |
| Producer | Dustin Wessel |
| Editors | egghorse, Cody Underwood |
| Rules Advisor | Sevenut |
| Official TTS Table | Jeremy Silliman, maths |
| Playtesting TTS Table | Troy Thompson |
Information on this page is transcribed from the official PDF file with minor edits to grammar for clarity.