[Runequest] Armour in Mongoose RuneQuest Considered Harmful

[Lev Lafayette]

I thank Phil Hibbs for bringing this to my attention; the modelling and
any errors in arithmetic are my own. Originally posted at
runequest at rpgreview.net; feel free to pass on to interested parties.

Let's take two example generic fighters; Red Fox and Green Knox who have
15 in their physical characteristics (STR, DEX, CON and SIZ) and 10 in
their mental and social characteristics (POW, INT, CHA).

They're both townsmen who have have prior experience as soldiers; so
they have 50% in Sword. They're using Bastard Swords 2-handed (1d8+1,
4AP, 12 HP). They both have three actions and reactions per round.

The only difference is that Red Fox wears no armour and Green Knox is
decked out in rather expensive full plate, which gives him 6 point
comprehensive armour, but also -42% in all DEX-based skills; including
attacking and parrying, which effectively reduces his ability in both
these actions to a mere 8%.

(In the last playtest version, 1.4, of Mongoose's RQ the modifier for a
full suit of plate was -20% which would have made the value 30% to
attack and parry for Green Knox, rather than 8%; it seems yet another
11th-hour decision was made which I have hitherto overlooked).

On this basis Red Fox will hit Green Knox more than six times as often
than the Knox hits Fox. Furthermore, on those rare blows that actually
land from Green Knox, Red Fox will parry one in every two of them,
whereas Green Knox will manage to parry a mere one in twelve of the
relative multitude coming from the Fox. In other words, the Red Fox will
hit successfully five in every twelve blows (50% * 0.92) , whereas poor
Know will manage but one in twenty-five (8% * 0.5).

Things indeed look grim for Knox! "But", one may ask, "what about Knox's
vastly superior armour? Surely the longstanding rule of RuneQuest was
that armour made you somewhat easier to hit, but much harder to damage?"

Well, a bastard sword in two-handed use does an average of 5.5 points of
damage, with a range of 2-9. Knox's plate of 6 points will block average
blows; but not all blows are average - a roll of 6 (7 points), 7 (8
points) or 8 (9 points) will be sufficient to cause damage. That is,
37.5% of blows landed. Overall Fox gets a (50% * 0.92 * 0.375) much
reduced 17.25% chance of hitting in a way that causes damage, and the
average damage received is 2 points with a range of 1-3. Green Knox
obviously causes damage every time he hits (4%) causing average damage
of 5.5 points.

Or, expressed proportionally, Red Fox has a 34.5% chance per action of
causing a point of damage, whereas Green Knox has a 22%.

The conclusion cannot be avoided. Wearing plate armour in Mongoose's
version of RuneQuest is dangerous to your character's health. They will
die approximately 50% faster than a character who does not.

The moral of the story is this: When you make a game rule, model it
before implementing it.

"Red Fox, our game is done, sir."