A Beastboss is a special type of Ork Warboss who has decided to go full native and lead a Beast Snagga clan. Like their 'modern' contemporaries, Beastbosses appear when enough Beast Snaggas come together to form an army of their own, or at least start asserting dominance over mobs of ‘lesser’ Boyz.
Decked in the spoils of their greatest kills and rippling with muscle, scar tissue, and bad attitude, Beastbosses lead from the front lines and look for the biggest, meanest prey they can find to bring down with their claws.
In a possible case of GDubs being extremely uncreative with their character design, the beast boss looks suspiciously like an Orruk megaboss (albeit an extremely kit bashed version), right down to sharing the exact same pose and sporting the iconic skull on their right shoulder.
Because of their comparatively slightly lower tech-basis, a Beastboss is usually armed with a Beastchoppa and a Beast Snagga Klaw. For a 'sidearm', he has a shoulder-mounted Shoota aimed and fired by a Targeting Squig.
On the tabletop, the Beastboss can be found on two varieties. The first is the regular old Beastboss on his good 'ol legs. He is basically the Beast Snagga edition of the Warboss, meaning he'll only be useful if you focus your army on those newfangled greenskinz. He's not something to sneeze at though, because while his only ranged weapon is a measly shoota that hits on a 4+, his melee weapons (a Beastchoppa with AP-2 and D2 and a Beast Snagga Klaw with S+4 AP-3 D2) are extremely powerful, especially when focusing on what Beast Snaggas do best: Killing big things. He is your more "budget" Warlord option, and a good one for all that.
The second version of the Beastboss is mounted on a Squigosaur. For an extra 50 points, this monstrosity not only has 9 wounds (just enough to still be eligible for the Look Out Sir rule) but also reduces all incoming damage by 1. Aside from being totally awesome, the practical reason you'd take this variant is because of the squigosaur's own jaws, which give three extra attacks: each attack is fully capable of swallowing a Terminator whole, especially if you roll a 6 to wound and score 3 mortal wounds. The mounted Beastboss is still armed with a Beastchoppa but loses the Beast Snagga Klaw, presumably because he needs at least one hand free to control the Squigosaur. He is also armed with a slugga instead of a shoota, and may take a Thump Gun if desired.
As a Warboss, the Beastboss can of course use the Call Da Waaagh! ability. His Beastboss aura also allows friendly Beast Snagga Core and Beast Snagga Character units within 6" of him to add +1 to each melee attack's hit roll (including himself). And as a Beast Snagga, don't forget that your Beastboss also gains an additional +1 to hit with both ranged AND melee attacks when targeting monsters and vehicles.