Random Explanations for Things I

Why are Orcs green?

Photosynthesis. Orcs draw in energy from the sun as they fight, which helps them stay cool (their resting body temperature is actually lower then humans) and get energy. This is also why orcs like to fight mostly naked- the speed and strength gained from the sun is more beneficial to them then what little protection armor can provide.

How can trolls regenerate infinitely?

Well in my opinion, they can't. That whole “capture a troll and slice off bits of meat for infinite source of food” isn't really how I imagine troll regeneration working. But the same as orcs- they photosynthesize to gain energy. Trolls are often green, right? Perhaps this energy is just expended instantly instead of saved up as glucose.

Why is gold and stuff valuable in a world with magic and alchemy?

Because it's the one thing alchemy can't make easily. The ability to turn lead into gold is highly sought after, and despite all the effort and lore it just doesn't work. Gold and gems are one of the few things that magic can't fake or conjure more of, hence it retains its value even in a world with crazy sorcerers, cleric healers, and alchemical forgeries.

Why do Taverns have individual rooms like a hotel? Isn't that an anachronism?

It might be in the real world, but not in the fantasy world. With wizards trying to study their glowy spellbooks in the middle of the night, being of different races trying to adjust to each others presence (like a dwarf's loud snoring), and the coming and going of adventurers with expensive and powerful gear they need to keep secure- it only makes sense that taverns have developed beyond common rooms with individual beds, walls, and locked doors.

If this is fantasy Medieval Europe, why are there potatoes?
Literally who cares.

Why would a dragon ever land to fight? 
Dragons are exceptionally prone to arrogance. They want to rend their enemies apart with claw and tail, not just with fire. They like getting blood on their claws, or scooping up the occasional knight as a nice snack. Or you could say it's because they're like lizards in that they use similar muscle groups to work parts of their body- they may need to land to breathe on occasion, or it could be they breathe fire unless landed, because their lungs can't expand when they are in flight.

Why can certain fighting moves only be used a X times per day?

Esoteric energy reserves. Specifically, this applies to special fighting or martial moves with daily limits, as to explain why they are limited. “Getting tired” is one excuse but doesn't really work considering the rest of the fighter's moves or actions are not inhibited in any way. So I explain it as special, esoteric energy reserves inside the body, cultivated by martial training. Everyone has trace elements of these energies, you just need to expand them through intense training and diet- so it's not magical. At least not magical for the fantasy universe. You could call it chi or whatever but I prefer to keep it a little more vague- chi is more of a full body thing, but I digress.

Why does Gold give XP?

It's an abstracted measure for how “good” you are at your job- recovering treasure from dungeons. The amount of gold you bring back is a good indication of how successful you are- Fighters are like the bodyguards, Thieves disarm the traps and scout ahead, Wizards are the problem solves, etc. It's a tightly knit group working together towards a common goal.

Oh- you wanted an in-universe reason? It's because the Gods smile upon you for getting your wealth back from the children of the Red God. All the money in dungeons was stolen from your people first.

Why do magic items have “once per day” limits instead of 24 hours or whatever?

It's because of the Time Between.

How did humans evolve in a world full of super powerful monsters and shit?

They didn't, Gods made them. Humans came into being at the same time as their technology- iron and clothes and farms all existed from the get go, there were no hunter gatherers. Or if you like the more civilization = evil take; man USED to be much stronger- the first men were larger, more powerful, and greater in every way to current man. The old bloodlines of the first men are watered down now; but sometimes they are what lead to great men; standing tall even among the decay.

If there are animal people like sheep and lizards, but sheep and lizards still exist, what is the “people” versions relationship to the animals?

Hopefully platonic.