How would I make a Riding Ram or Riding Boar?

[ElyasRavenwood]

I am thinking of making a dwarven cavalier or paladin.

I would like an alternate animal to a horse. I would like to put together a riding ram like in World of Warcraft....or a riding boar, like the mount Dain had in Battle of the Five Armies.....

How would I go about changing the size of a ram or boar so they are big enough to be a mount for a Dwarf with the Pathfinder rules?

Thanks

[Claxon]

You don't need to, they already exist. The Ram grows to medium size at 4th level, as does the boar.

All you need to do to ride one at that point is take the feat Undersized Mount.

[Adjoint]

Rams and Boars become Medium on lvl 4, so you can use them then with Undersized Mount.

A friendly GM may let you reflavor another animal companion (for example auroch or war bull, or some kind of megafauna) as a some kind of dire ram, suitable for riding.

Otherwise you may look for magical ways to permanently enlarge your mount (item with a permanent Animal Growth is an obvious one, but it would be expensive).

[Sensten]

Undersized Mount, as others have said. Dire Collar can make your companion bigger for a minute, pretty cheap if you wanted to buy a bunch and just use them during combat.

I second reflavoring another mount. In terms of similarity, a Styracosaurus gets all the same abilities as a boar (llv, scent, gore, ferocity). Just call it a dire boar. There's nothing quite the same as a Ram (nothing else gets improved bull rush) but a Megaloceros is pretty close.