Imojin's mount, Whiskers
ratfolk racial features:
Ability Score Racial Traits: Ratfolk are agile and clever, yet physically weak. They gain +2 Dexterity, +2 Intelligence, and –2 Strength.
Inspiring Rush Your charge inspires nearby companions to new heights of daring. Benefits: Once per day when you make a charge attack, you gain a +1 trait bonus on both your attack and damage rolls, as do any allies who make a charge attack before the beginning of your next turn.
Lightning Rider Benefit: When mounted and making a charge, your mount’s speed is increased by 10 feet. You must have the Mounted Combat feat to take this trait.
Indomitable Faith You were born in a region where your faith was not popular, but you still have never abandoned it. Your constant struggle to maintain your own faith has bolstered your drive. Benefit: You gain a +1 trait bonus on Will saves. bonus trait from Hakime, chronicle #17.
Mounted Combat (Combat) You are adept at guiding your mount through combat. Prerequisite: Ride 1 rank. Benefit: Once per round when your mount is hit in combat, you may attempt a Ride check (as an immediate action) to negate the hit. The hit is negated if your Ride check result is greater than the opponent’s attack roll.
Precise Strike (Combat, Teamwork) Prerequisites: Dex 13, base attack bonus +1. Benefit: Whenever you and an ally who also has this feat are flanking the same the creature, you deal an additional 1d6 points of precision damage with each successful melee attack. This bonus damage stacks with other sources of precision damage, such as sneak attack. This bonus damage is not multiplied on a critical hit.
Ride-by Attack (Combat) While mounted and charging, you can move, strike at a foe, and then continue moving Prerequisites: Ride 1 rank, Mounted Combat. Benefit: When you are mounted and use the charge action, you may move and attack as if with a standard charge and then move again (continuing the straight line of the charge). Your total movement for the round can’t exceed double your mounted speed. You and your mount do not provoke an attack of opportunity from the opponent that you attack.
cavalier class features:
Weapon and Armor Proficiency Cavaliers are proficient with all simple and martial weapons, with all types of armor (heavy, light, and medium) and with shields (except tower shields).
Challenge (Ex) Twice per day, a cavalier can challenge a foe to combat. As a swift action, the cavalier chooses one target within sight to challenge. The cavalier’s melee attacks deal extra damage whenever the attacks are made against the target of his challenge. This extra damage is equal to the cavalier’s level. The cavalier can use this ability once per day at 1st level, plus one additional time per day for every three levels beyond 1st, to a maximum of seven times per day at 19th level.
Challenging a foe requires much of the cavalier’s concentration. The cavalier takes a –2 penalty to his Armor Class, except against attacks made by the target of his challenge.
The challenge remains in effect until the target is dead or unconscious or until the combat ends. Each cavalier’s challenge also includes another effect which is listed in the section describing the cavalier’s order.
A cavalier gains the service of a loyal and trusty steed to carry him into battle. This mount functions as a druid’s animal companion, using the cavalier’s level as his effective druid level. The creature must be one that he is capable of riding and is suitable as a mount. A Medium cavalier can select a camel or a horse. A Small cavalier can select a pony or wolf, but can also select a boar or a dog if he is at least 4th level. The GM might approve other animals as suitable mounts.
A cavalier does not take an armor check penalty on Ride checks while riding his mount. The mount is always considered combat trained and begins play with Light Armor Proficiency as a bonus feat. A cavalier’s mount does not gain the share spells special ability.
A cavalier’s bond with his mount is strong, with the pair learning to anticipate each other’s moods and moves. Should a cavalier’s mount die, the cavalier may find another mount to serve him after 1 week of mourning. This new mount does not gain the link, evasion, devotion, or improved evasion special abilities until the next time the cavalier gains a level.
Order (Ex) At 1st level, a cavalier must pledge himself to a specific order. The order grants the cavalier a number of bonuses, class skills, and special abilities. In addition, each order includes a number of edicts that the cavalier must follow. If he violates any of these edicts, he loses the benefits from his order’s challenge ability for 24 hours. The violation of an edict is subject to GM interpretation. A cavalier cannot change his order without undertaking a lengthy process to dedicate himself to a new cause. When this choice is made, he immediately loses all of the benefits from his old order. He must then follow the edicts of his new order for one entire level without gaining any benefits from that order. Once accomplished, he gains all of the bonuses from his new order. Note that the names of these orders might vary depending upon the campaign setting or GM’s preference.
Members of these orders are not necessarily bound together, but some organizations do exist that are comprised of cavaliers that all belong to one specific order.
Tactician (Ex) At 1st level, a cavalier receives a teamwork feat as a bonus feat. He must meet the prerequisites for this feat. As a standard action, the cavalier can grant this feat to all allies within 30 feet who can see and hear him. Allies retain the use of this bonus feat for 3 rounds plus 1 round for every two levels the cavalier possesses. Allies do not need to meet the prerequisites of these bonus feats. The cavalier can use this ability once per day at 1st level, plus one additional time per day at 5th level and for every 5 levels thereafter.
Cavalier’s Charge (Ex) At 3rd level, a cavalier learns to make more accurate charge attacks while mounted. The cavalier receives a +4 bonus on melee attack rolls on a charge while mounted (instead of the normal +2). In addition, the cavalier does not suffer any penalty to his AC after making a charge attack while mounted.
Expert Trainer (Ex) At 4th level, a cavalier learns to train mounts with speed and unsurpassed expertise. The cavalier receives a bonus equal to 1/2 his cavalier level whenever he uses Handle Animal on an animal that serves as a mount. In addition, he can reduce the time needed to teach a mount a new trick or train a mount for a general purpose to 1 day per 1 week required by increasing the DC by +5. He can also train more than one mount at once, although each mount after the first adds +2 to the DC.
Order of the Beast features:
Order of the Beast (ACG)
A cavalier who belongs to this order serves nature in all its forms. These cavaliers believe that animals make the most loyal companions, and keep close to woodland creatures.
Edicts: An order of the of the beast cavalier must strive to protect nature—including animals and magical beasts—from the encroachment of civilization and from those that seek to harm it. He can slay enraged animals and magical beasts only when attempts to calm or pacify them fail.
Challenge: Whenever an order of the of the beast cavalier issues a challenge, his mount gains a +1 circumstance bonus on melee attack rolls against the target of his challenge whenever the cavalier is threatening the target. This bonus increases by 1 for every 4 cavalier levels.
Class Skills: An order of the beast cavalier adds Knowledge (nature) and Survival to his list of class skills. When the cavalier uses Survival to follow tracks, he gains a bonus on the check equal to 1/2 his cavalier level (minimum +1).
Order Abilities: An order of the beast cavalier gains the following abilities as he increases in level.
Wild Empathy (Ex)
At 2nd level, the cavalier can improve the attitude of an animal. This ability functions as the druid ability of the same name. The cavalier uses his level as his effective druid level when using this ability.
Wild Mount Shape (Su) At 8th level, an order of the of the beast cavalier gains the ability to turn his mount into a different Medium or Large animal and back again once per day. His options for new forms include all creatures with the animal type. This ability functions as beast shape II, except as noted here. The effect lasts for 1 hour per cavalier level, or until the cavalier chooses to change his mount back. Changing the mount’s form (to a different animal or back to normal) requires the cavalier to touch his mount as a standard action that does not provoke an attack of opportunity. The form chosen must be that of an animal the cavalier is familiar with. The mount does not change size, but does receive the bonuses (not the penalty) presented in beast shape II for the Large animal.
The cavalier can use this ability an additional time per day at 10th level and every 4 levels thereafter (to a maximum of four times per day at 18th level).
At 15th level, the cavalier can use wild mount shape to change his mount into a Medium or Large dragon. When taking this form, the cavalier’s wild mount shape now functions as form of the dragon I, except as above.
Ferocious Charge (Ex) At 15th level, the cavalier is the embodiment of nature’s fury. When the cavalier charges a creature, he can attempt an Intimidate check to demoralize his enemy as a free action. If he succeeds, the target is frightened.
Monster Codex p.177, which according to 'additional resources', is legal for play:
"A ratfolk with the animal companion, mount, or similar class feature can select a riding rat as her mount.
Riding Rat Companions:
4th-Level Advancement: AC +2 natural armor;
for this adventure only : potion of cure light wounds, mw sap
+1 lance [dice=to hit]1d20+7[/dice] [dice=dmg if hits]1d6+4[/dice]