Achilles' Heels

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A special weakness that can be exploited to cause defeats easier than can be done by using the other means available.

Many of the more difficult enemies in games can more easily, or in some cases only, be defeated by a special form of attack. These kinds of enemies have Achilles' Heels, special vulnerabilities that players can use to their advantage if they can locate it or gain knowledge about it. More rarely, the avatars or characters under players control have Achilles' Heels and then these need to be protected or kept secret.


The final boss monster in Half-Life can only be killed by first destroyed a number of crystals in the environment and then hitting a small gem inside its head. In The Legend of Zelda series and the Super Mario series, boss monsters (and some enemies) can usually only be defeated by special actions, such as grabbing hold of the enemies' tail and spinning around rapidly or hitting the enemies' so that it shows a vulnerable spot and then hitting that spot.

The idea of placing your soul or heart in a jar to become unkillable as long as the jar is not destroyed is a common feature in folklore. Both Dungeons & Dragons and GURPS have spells that provide this effect to players or their enemies.

The Mansions of Madness can be said to use Achilles' Heels since the players' controlling investigators do not know the winning condition and all enemies can keep spawning until the condition is revealed.

Using the pattern

The design of Achilles' Heels requires the presence of a complete Invulnerability but then makes this incomplete by inserting a Vulnerability - for this reason Achilles' Heels both modulates and is in conflict with Invulnerabilities. The two main design choices regarding Achilles' Heels is who has them and what is required to exploit them.

While Avatars and Characters under players' control can be given Achilles' Heels it is more common to give it to Enemies, and Boss Monsters specifically, since letting players have nearly invulnerable Focus Loci can make challenges too easy.

Making use of Achilles' Heels may need specific Powers, Tools, or Weapons and since this gives these an additional or specific purpose, Achilles' Heels modulates these patterns. Aim & Shoot or Timing can also be needed to exploit Achilles' Heels, and these may all be combined to create more Challenging Gameplay when Enemies have the Achilles' Heels.

Interface Aspects

Diegetically Outstanding Features can be used to let players more easily identify Achilles' Heels during interaction with those that have them. In other circumstances, other types of Clues can be used - for example information divulged during Cutscenes.


Achilles' Heels are a form of Vulnerabilities to otherwise invulnerable entities. By being the only way to defeat or Damage these entities, Achilles' Heels change how Combat or other activities related to Eliminate or Overcome goals can be achieved. The consequences of Achilles' Heels depend one if they belong to an Avatar or Character under a player's control or to his or her Enemies. One of the effects that does however not depend on who has the them is that secret Achilles' Heels, or those that cannot be exploited due to missing Powers or Weapons, are likely to lead to Repeat Domination. For this reason having information about Achilles' Heels is Strategic Knowledge, and likely to lead to both Strategic and Tactical Planning to either exploit or protect them.

In the case of Enemies that have Achilles' Heels (most common for Boss Monsters), these provide Challenging Gameplay in that they require players to identify a specific Vulnerability in otherwise invulnerable opponents. Trying to identify the exact nature of the Achilles' Heels are Gain Information goals and trying to achieve them is likely done through Experimenting or Puzzle Solving. The actual actions required to win over an Enemy with an Achilles' Heel is likely to provide Varied Gameplay.

When players' Avatars, Characters, or Units have Achilles' Heels, not letting others know about them leads to Conceal goals. If or when they are revealed, protecting them becomes a form of Evade goal.


Can Instantiate

Repeat Domination, Strategic Knowledge, Strategic Planning, Tactical Planning

with Enemies

Challenging Gameplay, Experimenting, Gain Information, Puzzle Solving, Varied Gameplay

with Avatars, Characters, or Units

Conceal, Evade

Can Modulate

Avatars, Boss Monsters, Characters, Combat, Damage, Enemies, Eliminate, Invulnerabilities, Overcome, Powers, Tools, Weapons

Can Be Instantiated By

Invulnerabilities together with Vulnerabilities

Can Be Modulated By

Aim & Shoot, Clues, Cutscenes, Diegetically Outstanding Features, Timing

Possible Closure Effects


Potentially Conflicting With



An updated version of the pattern Achilles' Heels that was part of the original collection in the book Patterns in Game Design[1].


  1. Björk, S. & Holopainen, J. (2004) Patterns in Game Design. Charles River Media. ISBN1-58450-354-8.