While Toothless and I were brainstorming possible concepts for the future KoT episode based off of "The Grave Robbers", the subject of the Krillitane homeworld was brought up.
A quick search on Tardis Index File revealed that there is no canon information concerning their planet. Obviously it will have to be fanoned.
Doing some quick solo brainstorming, I have come up with a couple of concepts for the Krillitane homeworld, which I will hereby refer to as Krillith simply because that sounds cool to me. I request input on which of these sounds best for our purposes.
Concept 1: The Oft-Conquered World
In this concept, Krillith has historically been a world rich in resources, and located in a strategic position in space. Because of this, the planet has been occupied over the centuries by a wide variety of alien races. By now the planet is bleak and desolate, devoid of most life.
This concept is interesting mainly because it can explain the orogins of the Krillitanes a bit better. The Krillitanes were enslaved many times, and formed a close-knit familiar society as a means of holding themselves together. Titles such as "brood-mother", or the referring of another male Krillitane as "Brother" could both be explained thus. Even better, it is possible that past resistance movements have developed bio-augmenting technology against their invaders. Eventually the desire to harvest new anatomical "models" led them to leave their homeworld and off to conquer other planets--meaning that they became the very thing they spent so much of their history fighting against.
Concept 2: Bubble of Monsters
I like this version better, in part because it holds more opportunities for games.
Here, the Krillitanes developed bio-augmenting technology without any outside interference, solely because they had a culture that emphasized self-perfection. As they grew to take over their world, they began to augment other native animals in the same way, altering them to suit their specific needs. For example, they raise morbidly obese herbivore creatures as a food supply. They might even use augmented plants as an outer layer on their ships--lichen like plants might have been augmented to absorb cosmic rays to power the ship. The creatures are raised in massive ecobubbles dotted all over Krillith, where groups of species exist in a sort of island ecosystem specifically steered towards a certain result. As I said, this seems to me to be the best for HotM purposes--not only could you have awesome games where the players travel through systems of ecobubbles, but Krillitane characters could have access to specially augmented pets.
Well, those are my ideas. Be sure to comment and tell me which you like better, or share any concepts you've come up with.