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\title{\textit{Dungeons \& Dragons} house rules}
\author{Mark Wooding}

\begin{document}
\maketitle

\section{Introduction and notation}

For the sake of brevity in the following descriptions, character ability
scores, and the usual modifiers are described using the notations shown in
tables~\ref{tab:ability-abbr} and \ref{tab:ability-mods}.

\begin{table}
\linewidth = 0.5\linewidth
\hsize = 0.5\hsize
\hbox\bgroup
\vbox\bgroup
\begin{tab*}{ability-abbr}{Ability notation}{Mcl}
  \th{Abbr} & \th{Ability} \\ \hlx{vhv}
      S     & Strength \\ \hlx{+}
      I     & Intelligence \\ \hlx{+}
      W     & Wisdom \\ \hlx{+}
      D     & Dexterity \\ \hlx{+}
      C     & Constitution \\ \hlx{+}
      H     & Charisma \\ \hlx{+}
      P     & Prime requisite \\ \hlx{+}
      A     & Some general ability \\
\end{tab*}
\egroup
\vbox\bgroup
\begin{tab*}{ability-mods}{Ability modifiers}{cMrMr}
  \th{Ability} & \th{Mod} & \th{Reduced} \\
     $(A)$     & (\delta A) & (\epsilon A) \\ \hlx{vhv}
       3       &     -3     &     -2       \\ \hlx{+}
     4--5      &     -2     &     -1       \\ \hlx{+}
     6--8      &     -1     &     -1       \\ \hlx{+}
     9--12     &      0     &      0       \\ \hlx{+}
    13--15     &     +1     &     +1       \\ \hlx{+}
    16--17     &     +2     &     +1       \\ \hlx{+}
      18       &     +3     &     +2       \\
\end{tab*}
\egroup
\egroup
\end{table}

\section{Experience and advancement}

\begin{enumerate}

\item Bonus experience points for high prime-requisite ability scores are
  \emph{not} awarded.  Characters with strong PRs are already at an advantage
  and shouldn't also make accelerated progress through levels.

\item Experience points are \emph{not} awarded to characters on the basis of
  treasure obtained.  It's hard to see why characters should be rewarded
  merely for stuffing gold down their trousers.

\item To compensate for this, experience points for monsters defeated are
  multiplied by 5.

\item Experience points for monsters defeated are calculated according to the
  revised table in the \emph{Master} set.

\end{enumerate}


\section{Character classes}

\begin{enumerate}

\item Player characters may be Mystics; neutral Clerics may become Druids at
  level~9.

\end{enumerate}


\section{Magic and ability scores}

In order to reward spell-casters with strong PR scores, their spells are
strengthened as follows.  (Recall that $P$ stands for the character's prime
requisite.)

\begin{enumerate}

\item Dice (up to $\dice{d20}$) rolled for damage (or healing) caused by a
  spell are modified by (up to) $\delta P$ in the caster's favour.
  Percentile dice are modified by (up to) $5\delta P$ in the caster's favour.
  This will \emph{not} increase a roll beyond the original bounds, but makes
  it more likely that the bounds will be reached.  For example, a
  seventh-level Magic-user with $I = 16$ casts \emph{magic missile}; each of
  his missiles causes 4--7 points of damage, computed as $\min(7, \dice{1d6}
  + 3)$.  Spells such as \emph{fire ball} have each die modified
  individually.\footnote{%
    The distribution this induces is slightly better shaped than the one you
    get by applying a modifier to the sum of the dice, but has the curious
    property of being non-monotonic.  This is unlikely to be a problem in
    practice.}

\item Saving throws against spells are penalized according to the caster's
  $\delta P$.  Suppose our Magic-user casts \emph{fire ball}.  A victim in
  the blast radius must save versus spells at $-2$ or take $\dice{7d6}$\,hp
  of damage, with each die modified upwards by two points.  If the save is
  successful, half damage is taken, as usual.

\end{enumerate}


\section{Saving throw adjustments}

Saving throws are modified by a character's ability scores.  Which ability
applies is dependent on the action the character takes to avoid the effect.
Sometimes several abilities apply; then \emph{all} the modifiers are taken
into consideration.
\begin{itemize}

\item Saves versus poison are usually modified by the character's
  Constitution.  Similarly, saves versus paralysis (e.g., for a Ghoul's
  touch) are modified by $\delta C$.

\item Saves against magical effects are usually modified by Wisdom.  Not all
  saving throws against magical effects are Saves vs Spells: for example, the
  Save vs Turn-to-Stone for gazing at a Medusa is modified by $\delta W$.
  Similarly, the Save vs Death Ray for the \emph{finger of death} spell is
  modified by $\delta W$.

\item Saves versus Dragon breath are usually modified by Dexterity.  The Save
  vs Paralysis for being knocked over by a Dragon's tail is also modified by
  Dexterity.

\end{itemize}


\section{Weapons and combat}

The weapon master rules in the \emph{Master} set are used.  The following
modifications are made to the system.

\begin{tab}{mastery}{Mastery adjustments}{llMrMr}
  \th{Level}   & \th{Abbr}  &  M & \delta M    \\ \hlx{vhv}
  Unskilled    & US         &  0  & -2         \\ \hlx{+}
  Basic        & BS         &  1  &  0         \\ \hlx{+}
  Skilled      & SK         &  2  & +1         \\ \hlx{+}
  Expert       & EX         &  3  & +2         \\ \hlx{+}
  Master       & MS         &  4  & +3         \\ \hlx{+}
  Grand Master & GM         &  5  & +4         \\
\end{tab}

\begin{enumerate}

\item Magic-users may use the dagger and staff, and thrown objects.

\item All character classes may fight unarmed.  Characters begin with Basic
  mastery at both Striking and Wrestling; this does not cost a mastery slot.

\item Characters can acquire mastery in the (normal) shield, to improve the
  armour-class benefit it provides.  All character classes who can use a
  shield are automatically considered to have Basic mastery in its use; this
  does not cost a mastery slot.

\item Fighters and Mystics receive four mastery slots at level~1; other
  humans receive two slots.  Demi-humans can use all weapons at Basic mastery
  at level~1, and receives no mastery slots.  A level~1 character may
  \emph{not} spend two slots on the same weapon (to reach Skilled mastery or
  better).

\item Fighters, Mystics, Dwarves and Halflings receive an additional mastery
  slot at level three, and again every third level after that (i.e., at
  level~3, 6, 9,~\dots).  Clerics, Thieves and Elves receive an additional
  mastery slot at level four and again every fourth level after that.
  Magic-users receive additional an mastery slot at level five and again
  every fifth level after that.  All characters gain an additional mastery
  slot every 200\,000\,XP after maximum level.

\item The to-hit bonuses for weapon mastery are halved.

\item The morning-star and flail (one- and two-handed) are added, as
  additional weapons for Clerics.

\item Characters do not lose initiative automatically for using a two-handed
  weapon.  Rather, a $-1$ penalty is applied to initiative rolls for using a
  `large' weapon; a $+1$ bonus applies for using a `small' weapon; see the
  weapons table for sizes.

\item The bastard sword is designed to be used one- or two-handed.  A
  character who acquires mastery in the use of the bastard sword learns how
  to use it \emph{both} one- and two-handed to best effect.  A character with
  an empty off-hand can decide whether to wield the bastard sword one- or
  two-handed in each combat round with no penalty.  An off-hand wearing a
  cestus still counts as empty for this purpose.

\item A weapon can be used in a character's off-hand.  To use a weapon in the
  off-hand effectively, one must learn how to use it to complement the main
  weapon -- it can't be learned in isolation.  While one might acquire
  mastery of the normal sword, say, as a main weapon, one would have to
  acquire mastery in the use of a dagger as an off-hand weapon
  \emph{separately} with (say) the sword and the morning-star.  A character
  Unskilled with an off-hand weapon strikes at a $-4$ penalty (and does half
  damage, as usual).\footnote{%
    This ruling provides a major advantage to demi-human characters, since
    demi-humans are considered to be able to use all weapons at Basic
    mastery.}

\item One- and two-handed flails are different weapons, and a character must
  spend mastery slots on them separately.  However, they are \emph{related}
  weapons -- see below.

\item A character with a level of mastery $M$ with some weapon may attempt to
  use a \emph{related} weapon; the skills don't transfer completely, but
  related weapons (see table~\ref{tab:weap-related}) can be used with mastery
  level $\lfloor M/2 \rfloor$.
  This also applies to the use of a familiar off-hand weapon with a related
  main weapon.  The use of a merely related off-hand weapon, even with a
  familiar main weapon, is always considered Unskilled.
  \begin{tab}{weap-related}{Related weapons}{ll}
    \th{Weapon}       & \th{Related weapons}             \\ \hlx{vhv}
    Bow, long         & Bow, short                       \\ \hlx{+}
    Bow, short        & Bow, long                        \\ \hlx{+}
    Crossbow, heavy   & Crossbow, light                  \\ \hlx{+}
    Crossbow, light   & Crossbow, heavy                  \\ \hlx{+}
    Flail, one-handed & Flail, two-handed,;morning-star  \\ \hlx{+}
    Flail, two-handed & Flail, one-handed                \\ \hlx{+}
    Halberd           & Pike, pole axe                   \\ \hlx{+}
    Javelin           & Spear                            \\ \hlx{+}
    Morning-star      & Flail, one-handed                \\ \hlx{+}
    Pike              & Halberd; spear                   \\ \hlx{+}
    Pole axe          & Halberd                          \\ \hlx{+}
    Shield, horned    & Shield, knife; shield, sword     \\ \hlx{+}
    Shield, knife     & Shield, horned; shield, sword    \\ \hlx{+}
    Shield, sword     & Shield, horned; shield, knife    \\ \hlx{+}
    Spear             & Javelin; pike                    \\ \hlx{+}
    Sword, normal     & Sword, short; sword, bastard     \\ \hlx{+}
    Sword, short      & Sword, normal                    \\ \hlx{+}
    Sword, bastard    & Sword, normal; sword, two-handed \\ \hlx{+}
    Sword, two-handed & Sword, bastard                   \\
  \end{tab}

  Note that the property of being related weapons is \emph{not} transitive!

\item The \emph{deflect} ability makes high-level characters nearly
  untouchable, as many have noted.  The new definition allows an attack to be
  deflected if $\dice{1d20} + \delta D + \delta G$ (where $\delta G$ is the
  magical strength of the weapon used) is greater than the attacker's
  (adjusted) hit roll.  Deflection does not work against device-hurled
  missiles; it does work against thrown weapons.

\item Each involved character or monster rolls $\dice{1d6} - \epsilon E$
  every round to determine initiative.  Actions occur in ascending order of
  initiative rolls.  Ties indicate simultaneous action.

\end{enumerate}


\section{Alignment}

The idea of alignment as an observable property of the game world is absurd.
Alignment languages and the Cleric \emph{know alignment} spell are
abolished.


\section{Clerics}

\begin{enumerate}

\item Clerics who can Turn Undead creatures (with a `T' or `D' result) can
  optionally control them instead, as an Avenger.  This is considered to be
  an evil act.

\item The spell \emph{know alignment} is replaced by the AD\&D spell
  \emph{slow poison} as follows.

  \textbf{Slow poison} \\
  Range: touch \\
  Duration: $L$ hours \\
  Effect: Slows poison in the body of a creature \\[\medskipamount]
  Slows the effects of poison on an individual.  A creature can be affected
  even if supposedly killed by poison, in the previous $L$~turns.  The poison
  will remove one hit point per turn (though never reaching zero while the
  spell lasts).

\item Druids must still be Neutral.  Maybe I'll relax this later.

\item Clerics (and Druids) of level 9 or higher don't need to choose their
  first-level spells in advance each day; they may cast any combination of
  first-level spells up to the daily maximum.  At level~14, second level
  spells no longer need to be chosen in advance; similarly for third-level
  spells at level~18, fourth-level at~23, fifth-level at~27, sixth at~32 and
  seventh at~36.

\end{enumerate}


\section{Magic-users}

\paragraph{Background notes on spell books}
A standard spell book is an enormous thing.  My \emph{Dictionary of the
  English Language} (Johnson) weighs about 5\,kg.  \emph{Unearthed Arcana}
suggests 450\,cn; \emph{Sage Advice} (Dragon \#134) suggests 400\,cn --
backpack size.  This doesn't seem too far off.  \emph{UA} also suggests that
a standard book cost about 1000\,gp, which may be reasonable.  I don't
propose to apply the limits on capacity of spell books.

\emph{UA} also suggests travelling spell books, which are smaller somewhat
cheaper but with less capacity.  As stated above, I don't want a capacity
limit on standard books (the things are huge already!) but limiting
travelling books seems reasonable.

\begin{enumerate}

\item A standard spell book costs 1000\,gp, measures $15'' \times 9'' \times
  3''$ and has encumbrance of 350\,cn (due largely to bulk).  There isn't a
  practical limit on the number of spells it can store.

\item A travelling book costs 500\,gp, measures $9'' \times 6'' \times 1''$,
  and has encumbrance 60\,cn.  It can store ten spells; level is irrelevant.

\end{enumerate}


\section{Fighters}

\begin{enumerate}

\item Any Fighter may become a Paladin or Avenger, regardless of alignment,
  if the appropriate religious hierarchies accept him/her.

\end{enumerate}

\paragraph{For consideration}
Maybe it makes sense to allow neutral Fighters to become Druid-like -- giving
up the ability to Turn Undead for Druid spells along with the Cleric spells
already obtained for sufficiently high Wisdom.


\section{Thieves}

\begin{enumerate}

\item Die rolls for the Thief abilities Open Locks, Remove Traps, Move
  Silently, Hide in Shadows and Pick Pockets are adjusted by the $5 \delta
  D$.

\item Climb walls is affected by $\delta D$ (not $5 \delta D$).

\item Find Traps is affected by $5 \delta W$, as described below.

\end{enumerate}


\section{Searching}

\begin{enumerate}

\item Rolls on $\dice{1d6}$ for searches (e.g., for secret doors) are
  modified by $\epsilon W$.

\item Rolls on $\dice{1d20}$ for searches are modified by $\delta W$.

\item Rolls on $\dice{1d\%}$ for searches (e.g., for traps) are modified by
  $5 \delta W$.

\end{enumerate}


\section{Bugs found/fixed}

\begin{enumerate}

\item The rules for evasion in the wilderness are obviously wrong: more
  pursuers should have a better chance of catching a party than fewer.  I've
  attempted to fix the tables but I'm not completely thrilled with the
  result.  The AD\&D rules seem wrong too, so they're no help.

\end{enumerate}

\end{document}

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