Lol, butchery is quite the thing to be remembered by
I designed all systems in MO up to and including Dawn, excluding the flagging system which I "simply" reverse-engineered and the first magic school (Ecumenical) which was Henrik's. And of course the actual movement- and combat action design is Sebastian's. Henrik was always the guy with the vision for the game and decided which systems we needed, what to prioritize and in which order to do them. Me, Sebastian and Henrik usually brainstormed ideas for these together, and then I worked out the mechanics and designed them.
If I am to take credit for systems where I did both design and whole concepts/ideas it would be the skill system (structure of the system, the secondary skill tree and all learning skills, dynamic allocation of points, books etc. and a nice way of visualizing the whole thing which unfortunately was never implemented), races and blood-mixing, the material system / dynamic crafting of items (although only battle-oriented stuff like weapons and armors got in during the time, and with no dyeing or marks, no reprocessing, and only a placeholder version of "recipes" which were supposed to be much more interactive), extraction and alloying (though only a very basic alloying system was actually implemented), dynamic structures (bridges and interactive stuff), flora and fauna and their respective phylogenetic trees, creature genes for advanced breeding, Etherworld (and later Spiritism), the first iteration of territory control, and a couple of systems that were quite complex where unfortunately only the tip of the iceberg could be seen/utilized in game due to restrictions mostly having to do with the former GUI (food system, alchemy, fishing, dynamic item identification/assessment). The first iteration of NPC-faction behaviour (real-time AI and spawn structure placement, resource deposits (like chests)), and "key"-items and "door"-items and some other interactive features were also my concepts and designs - introduced with the Risar invasion.
Henrik has always been the visionary and leader of the whole crew. As the Creative Director I was responsible for all art, sound and game design (excluding combat action and offensive magic as I explained above) from start until some time after Dawn.
And yes, I wrote the vast majority of the lore and did the world design up until then (history, religion, races, magic, geography, geology, biology etc.). Most of it was non-official though. I've been away for quite some time, but I'm doing my best in contributing to the team with some stuff right now.