Houserule: Pets & Service Animals

I spent too long looking trying to generate a random horse system.  After taking a break from it, I thought about how to handle dogs (war, riding, hunting, and tracking), guard geese, hawks, elephants, and riding apes.  I decided I wasn't smart enough to get too into the weeds with them, and came up with this far simpler method to introduce variety to all kinds of adventurer's animal accomplices.

 Basically, just use these to put more of an emphasis on animals, and further differentiate them from each other.

Pets & Service Animals

This is for every kind of animal, from mounts to combat animals to familiars.

Tricks

"Unintelligent" animals (those with 1 or 2 intelligence, if it's quantified at all) can learn 2 tricks, smart animals learn 4.  They are triggered by a visual signal or a sound.  Trained animals are worth 25% more per trick they know.  If in doubt, assume an animal knows the tricks for the things it already does regularly.
 

Each trick takes 2d6 weeks to learn from an NPC.   PCs can try to train an animal: each check takes four weeks.  At the end of that period, the PC rolls a wisdom check
 

Here is a sample listing of tricks:

• Attack: Move and attack on their own when opportunity arises.

• Battle Trained: Does not check morale at the start of battle.

• Defend: Attack hostiles that get too close.

• Guard: Make noise when creatures it doesn’t know well gets too close.

• Hunt: Predators have a 1-in-6 chance twice per hour to capture game while traveling unencumbered.

• Knee-directed: Follow rider directions based on knee pressure.

• Leap: Jump over obstacles on command, even if they can’t see the other side.

• Rescue: Look for hidden or trapped people, pull them out if unconscious.

• Retreat: Withdraw from combat, returning to handler.

• Return Home: If the handler disappears or (for a mount) is unresponsive for an extended period, the animal will return to its most recent encampment, if there was one, then to its most recent permanent home.  

• Silent: Does not make noise until commanded otherwise.

• Sound-directed: Follow direction based on driver’s sounds.

• Stay: Don’t move from this position.  This trick is "free", 

Traits

For these rolls, roll an orange d6 and a purple d6*.  Use the lower die value.  Player chooses on a tie.
No re-rolls of duplicates.  Orange d6 is first entry for a number, purple d6 is second.  Traits don't stack: you can pick the same trait multiple times, but it only applies to the animal once, so if you roll clever twice, it only gets +1 to handling, morale, and surprise checks, and only gets one extra trick, not two.

Physical Traits (roll twice):

1. Mute: doesn’t make noise; Deaf: can’t hear.

2. Rotund: -5 ft. speed, +1d6 HP; Delicate: -1 to CON checks/saves.

3. Majestic: -1 on morale for creatures hit by it; Graceful: +1 to evasive AC and saves.

4. Lean: +1 to initiative, -1 to CON checks.; Solid: +10% load, +1 1d6 HP

5. Resillient: +2 to CON checks to avoid exhaustion and +1 morale checks;
   Sprinter: +5 ft. of movement, -2 to CON checks to avoid exhaustion.

6. Muscular: +1 dmg, +15% load; Tough: advantage on hit dice and CON saves, +1d6 HP.

Personality (roll twice):

1. Gluttonous: Eats even when full, needs a loyalty check to avoid being tempted by food, +1 trick;
   Skittish: Gain +1 on initiative, and evasion-based saves and -1 on morale.

2. Cunning: Aids allies against foes for either defense or attack;
   Observant: Advantage on surprise checks to to avoid hazards moving through hazardous terrain.

3. Stubborn: +1 morale and loyalty checks, -1 to handling checks;
   Loyal: +1 to morale checks, and will fight beside their master even if their master goes down.

4. Wild: -1 to handling and loyalty checks, +1 to morale;
   Anxious: -1 morale checks, +1 to initiative and surprise checks.

5. Reckless: +1 to initiative and morale checks, -1 to saves and AC;
   Cautious: +1 to saves and surprise checks. 

6. Clever: +1 to handling, morale, and surprise checks, +1 trick;
   Aggressive: +1 morale & initiative  checks and dmg.  -1 AC against enemies set for a charge.

 

Evaluating an Animal

Upon spending a turn inspecting an animal, a character can roll a d20 under their Wisdom to determine three lowest traits of that animal.  If they fail normally, they only learn of the lowest value physical and personality traits.  On a natural 20, they mistake one of the traits with the highest value for one of lower value as determined on the table above.  On a natural 1, they learn all four of the animal's traits.  This check will also detect symptoms of diseases, injuries, or poor care, although the vendor may try to hide this with short term tricks.

 

For example,  Frank is passing himself off as a teamster to infiltrate a warehouse.  As part of his interview, he is asked to pick out the qualities of a horse.  He spends a turn examining it, and fails his check.  The horse has the physical traits delicate (2) and solid (4), and the personality traits skittish (1) and stubborn (3).  Frank learns the animal is delicate and skittish, but not that it is solid and stubborn.

After twelve hours spent with an animal, an animal expert such as a teamster or drover will know all the animal's traits will.  It might take someone else 1d6+2 times as long.

Additional Optional House Rules for Animals

These rules complicate things further, so don't use them unless you're in a campaign which has lots of mounts or other animals.

 

Handling Checks are checks to see if an animal follows its handler's command. If your game doesn't have a system for this, I suggest this:

For each command, roll 2d6 roll below the animal's morale value:

• Add your charisma bonus to the animal's morale score.
• You succeed if it's what the animal already wants to do.
• Apply a -2 modifier if it's something the animal doesn't want to do.
•  If you don't have morale scores, assume the following morale scores: 
• Well-cared for animal: 9
• An average animal: 7
• An abused animal: 5
• "Intelligent animals" get a +1 morale bonus. 

Clerics

• Divine Blessing: When a cleric is choosing or is sent an animals associated with their deity, roll three times for each type of trait, the cleric's player chooses which two to keep.
• The first time each day a cleric's mount would take fatal damage, re-roll that damage roll. 

Fighters

• A mount cared for by their fighter for at least a month gains additional hit points equal to twice the fighter's level. 
• When a mounted fighter makes their save against an area of effect spell or effect, their mount takes no damage if the fighter makes their save.

Magic-Users

• For familiars, roll for three traits of each type,  the magic-user's player chooses which two to keep.
• Familiars are immune to spell effects while touching the magic-user unless the magic-user is killed or goes unconscious.
• Familiars automatically succeed on loyalty checks, and have advantage on morale checks.

Thieves

• For creatures a thief has had at least a month:
• The thief can teach additional tricks up to 50% more than the base number.  These tricks take twice as long to teach, and the animal will only do them for the thief who trained them.
• Thieves get a +2 bonus on checks to determine an animal's traits.

* They obviously don't have to be orange and purple, you just need to know which one corresponds to which color here.