Let's Read the 4e Monster Manual/Vault: Boar
Boars are real animals, so you probably know what they look like already. Boar-hunting was a very prestigious and difficult endeavor in medieval times, since real-world wild boars are deadly opposition for someone armed with a spear.
Still, the Monster Manual seems to think your typical PC party would have little trouble handling real-world boars, much like Asterix and Obelix. So it provides us with more extreme versions.
These exist only on the Monster Manual - while the Monster Vault has an appendix on animals, it doesn’t contain boars.
Dire Boar
Like a real-world boar, but bigger, meaner, and spikier. It’s a Large Natural Beast (mount). Creatures with the “mount” keyword confer special abilities to their riders. Not all beasts that can serve as mounts have the keyword - only those who grant these abilities to their riders. Early rules for mounted combat stated that PCs had to have the Mounted Combat feat to benefit from these mount powers, and mount stat blocks usually stated that the rider also had to have a minimum level. All of this had been done away with by the time the MV came out.
Indeed, dire boars can be domesticated as mounts, though even then they’re ill-tempered and tough to handle. They’re also the preferred mount for dwarven cavalry units. So yeah, dwarves have dire boar cavalry! It makes perfect sense when you think about it: the riders have a temper to match that of their mounts, and the mounts menace with spikes of bone.
Rules-wise, dire boars are Level 6 Brutes, have 85 HP, and move with Speed 8. They attack by goring with their tusks, which does extra damage against a prone target. When the boar is reduced to 0 HP, it gores one last time as a free action.
They’re also good at charging! A gore attack done as part of a charge does extra damage, pushes the target 2 squares and knocks them prone. So their preferred tactic is to charge someone and them gore them repeatedly while they’re down.
If used as a mount, the boar gets to make a gore attack in addition to the rider’s attack when the duo charges. The way I understand it, this gore attack also gets the charge benefit I described above.
Thunderfury Boar
The platonic ideal of a badass boar, native to the Feywild. It’s even bigger, even meaner, and even spikier than a dire boar. This boar is a Large fey beast, no mount keyword. You can’t truly domesticate these beasts, but clever fey sometimes keep them captive and release them in the general direction of people they want dead. They have Int 5 but no languages. Whether this means they’re super-cunning animals or actually sapient is left as an exercise for the GM.
The thunderfury boar is a Level 15 Brute with 182 HP and ground speed 8. It fights in much the same way as its cousing above, with goring charges followed by more goring, but it has a few differences aside from the increased damage. Its basic gore attack deals increased damage when the boar is bloodied, and its charges deal an extra 10 thunder damage on top of that. It also has an attack named Thunderfury, rechaging on 5-6, which from what I understand it is a big stomp that sends a shockwave around the boar. It’s a close burst 2 that targets Fort, does thunder damage and knocks prone. On a miss, it still deals half damage.
Encounters and Final Impressions
The suggested encounter is level 5, a dire boar and a party of 5 orc regulars (1 shaman, 4 berserkers). Having one of the berserkers ride the boar will give you the most bang for the buck when it comes to charging attacks.
The most awesome thing for me here was the bit about dwarven boar cavalry. I’m really tempted to stat up a unit of level 6 dwarven knights riding dire boars. Beware the charge of the 15th Thundertusks!