Next stage is an orc. Orcs are compared to dwarves and elves, yet they're taller than former and more muscular than latter. Almost hairless, with animal claws and short snouty noses, orcs are very strong and violent. They lose goblinish craftiness and more peoples features, instead being more couragous, strong and intimidating, more animalistic features with growth. They start to show trollish regeneration at times. Orcs are usually warlords and chieftains of trollkin warbands, lacking more civilized features of goblins but with enough brute strength and drive to rule.
Last known stage of trollkin is a troll. These are very varied in size, ranging from an ogre to small hill in size. They also lose characteristics of civilised humanoids, start to resemble beasts or mindless monsters more and more. They have unimaginable ability to heal and regenerate, sometimes turning against them in form of weird mutation and overgrowth. Trolls spend large portions of their time in meditative slumber, waken up by hunger and urge to destroy after which they hide back in their caves. It is assumed at some point troll's mind dissolves and it becomes new, fully grown mothercelium, which starts new, mutated and better fitted line of trollkin.
Notable mutations:
Hobgoblins - some groups of trollkin stop growing when they reach a stage between goblin and orc. These species are called hobgoblins, their nature is quite different than regular cousins. They keep goblinish craftiness and dexterity while also gain orcish strength and courage. It creates perfect environment for their hordes to fuel industry of war. They are usually biggest force in terms of local armies. Motherceliums is suspected to grow on battlefields after two hobgoblin groups battle each other.
Deep Kin - some kinds of trollkin living in deep underground caverns became better suited for such environment. Sharp senses, pale skin, more hunt-based than warfare lifestyle and greater deal of individualism from early stages of growth. They can be really resilient enemy yet underground in not most fertile place for motherceliums. Their lonely hunts rarely let them grow a lot, assumption is they bring leftovers to nests.
Rust Orcs - there is noted separate line of trollkin which produced rust-tinted orcs. These are very beastial and brutal and specifically set on finding other kinds of trollkin. They evolved into predator of their own cousins, often spoiling other motherceliums with their dead bodies to overtake them. They look like regular trollkin to non-rust ones - also goblin and troll stages don't carry rust characteristics which additionally complicates the spread. Gossip says some crafty wizard created them.