Let's try to do this.
(They told you it can't be done. They're right. Realistically, it can't. So, disclaimer: I'm going to employ industrial quantities of high-grade Improbability).
I had to play with "realize what this thing is". There's no reasonable way I can hand-wave an alchemist deducing nuclear fission. The best I think we can aim for is ...
What you're looking for is an emetic - a substance that induces vomiting. This is the specific reason why, as @Alberto Yagos already stated in his answer, suicide-by-pills doesn't always work - many pills are coated in a small amount of emetic so you'll throw them up if you take too many.
In the case of your poison, a large enough dose would cause you to ...
No seriously a cheap waterproof rain slicker or pair of rubber boots will bribe the average person very easily, waterproof materials were nonexistent. It is also really easy to demonstrate and you can buy them at a dollar store. The best they had at the time were merely water resistant materials which tended to stain since they were soaked in oil. ...
The question shows a misunderstanding of why the Middle Ages were medieval. It's not that the people who lived in those times did not know any better. They did. In particular, they had good Roman books about military strategy, tactics and logistics; for example, they had and they actually read Vegetius's De re militari; the book was copied over and over, and ...
Ten (or more) knights would grab him by the arms and legs, bind him in iron chains, and then chuck him in a dungeon.
No matter what kind of armor or melee weapon you have, you are still limited to the strength of one human; you will be overpowered almost instantly by a group of people.
There are numerous problems.
Diamonds are brittle
Hard, but relatively easy to crush, if you happen to hit just right. Armor would be crushed before your hero knows what happened. See Why does diamond have lower tensile strength than Iron? on Physics Stack Exchange.
Diamonds are flammable
Sure, it takes about 900 degrees Celsius to start diamond fire, but ...
Any craftsman during their journeyman years.
A journeyman is a craftsman who just completed their apprenticeship. There was a custom during the middle ages (especially in the German-speaking area) called the "Walz". Young craftspeople spent three years and one day with traveling to other cities, seeking contact to the locals of the same profession and ...
I practice early medieval (Viking) style semi-contact as a hobby. With blunt steel weapons not with some LARP toys. I can tell you how we deal with an enemy with a shield and then some historical methods I know. Now our fights are not entirely realistic, they do not devolve into fierce unarmed struggles, at the end, where we attempt to scratch out eyes and ...
Farmer, farmer, and farmer
Assuming it is independent and not a satellite settlement (a satellite community is far far more likely) there is only one job, farmer. there is not enough people to support specialized labor. (note farmer might be replaced with fisher in a coastal settlement)
Maybe, maybe they have a blacksmith, although a hundred is is a pretty ...
My character lives on a medieval world, and is a female knight, she is looking for marriage and is trying to look more attractive for potential candidates without losing too much protection.
I think you need to look at this differently.
Marriage, especially among the knighted classes, in medieval times was not primarily about looks (and not even in the ...
There are a few options:
Aluminum. Until modern times, it was essentially impossible to produce in any significant quantity, making it far, far, far more valuable than gold. It is also a useful metal in its own right, being strong and light. And it should break down within 500 years, so it won't leave any archeological evidence in the modern day. Price: ...
Inspired by Hosch250's comment
1- Carrier pigeons don't actually go to a any given location, they really just return to their nest.
2- Spoons have an annoying tendency to fall into soup bowls.
Take advantage of these two facts. Your pigeons are spoons on the outside but they're still pigeons on the inside, only very confused. Get another alchemist (surely ...
Put it another way:
Just let the prisoner out when he/she pays for his/her weight.
The prisoner opens the door, gets in, and closes the door. The door is automatically locked. The inner walls are all slimy/oily and slant inward at the top, so he cannot get a hold on them. There is a slot for coins. He/she puts one big coin for each pound and when the ...
Polish them to a mirror shine. Put one spoon with one operator on a tower within visible distance from another one. Invent coding that uses "long shines"-"short ones".
Important messages would still be sent by horse (because it's harder to stop a messenger on a fast horse) and frivolities can be sexted with Morse code.
EDIT The use of a horse is to ...
No technology is needed at all:
All horses move naturally with four basic gaits: the four-beat walk,
which averages 6.4 kilometres per hour (4.0 mph); the two-beat trot or
jog, which averages 13 to 19 kilometres per hour (8.1 to 12 mph)
(faster for harness racing horses); and the leaping gaits known ...
Modern soldiers are trained and equipped to modern warfare. They are next to useless for ancient warfare. At best, they wouldn't be better than any other piece-of-flesh to make for cannon-fodder and more probably than not they would be a dead weight to get rid off at the first opportunity.
Even handwaving the language problems that would render them ...
There's a lot of toxic metals. Most are toxic in fact (including iron technically, if you get enough of it). Almost all of them have issues though:
Mercury: One of the first metals many people think of when they are thinking of poisons. The problem here is quite simply that even those mercury alloys that are solid at room temperature (known as amalgams) ...
Consider a mountain pass.
In short, you need a small village located on a major road.
Possibly, your village is located near (on the only road leading to) a mountain pass. You mentioned the mountainous location, so it fits geographically, and such location will result in quite a bit of traffic (merchants, travellers) passing through. At the same time, the ...
Engineers, stone cutters, and masons were some of the widest travelers of the era, moving between castle and cathedral construction sites regularly, often staying for only a single season of work at a given site before moving to another when the local weather stopped work.
Boatmen also traveled long distances up and down rivers and canals moving cargoes of ...
Depressing, realistic version:
John Doe has major problems:
His modern skills are of little use in a medieval English village. The peasants don't care about numeracy or crazy ideas, they want somebody who can slaughter a pig or plough a field.
He has great difficulty communicating with the locals. Have a look at Shakespeare or Chaucer's English, and ...
Honestly, the best use of this would be to turn corpses (their and yours), waste, and the like into nice safe gold. Campaigning armies in medieval times suffered greatly from disease, and poor hygiene was a major part of that. The fewer dead bodies and other disease-spreading elements you have about, the better off you'll be.
Others have asked and answered these questions more than 2000 years ago. Just read literature about any pantheon of gods and you'll find a lot of great patterns.
Gods can be banished (from places or social gatherings, not from a plane of existence)
Gods can be imprisoned
Gods can be tortured (chain them to a rock and send a bird every so often to eat some ...
Make the Legend last through the ages
So, Merlin telemagicks to 5000 years ago, presents the sword-in-cement LEGEND to some fancy king. Then he rigs up some scenario where the sword is found. People try and fail to remove the sword, the legend spreads.
Merlin then causes some event (flood, landslide, magic POOFing, etc) to disappear the sword. The sword ...
Honestly the 'modern' military theory that would give Lord Gary the biggest advantage would be modern attitudes towards hygiene. It was extremely common in the time period you're talking about for a force to lose more troops to dysentery and other diseases than they lost in actual combat.
By taking a very firm attitude towards latrine maintenance and ...
One large hollow rock
One large pair of pliers
One loud voiced announcer of who is about to try to pull the sword out
Tunnel under the rock for your dwarf to get access, make sure he knows the name of the eligible person to release the sword for when the loud voiced announcer calls it out. All you need now is a mechanism ...
Merlin knows about metallurgy, and will place in the immediate surroundings of the rock (or even IN the rock) a sacrificial anode made of magnesium, aluminium, zinc or another suitable metal.
A galvanic anode is the main component of a galvanic cathodic protection (CP) system used to protect buried or submerged metal structures from corrosion.
By simply ...
Let's consider a real historical example
Let's fix the historical period to the 14th century, and let's say that "language 1" is French and "language 2" is Romanian. Both French and Romanian are descended from Latin (which is thus "language 0"), and in the 14th century, they had had no contact for about 1000 years. No 14th century Frenchman spoke Romanian, ...
Related to cmaster's solution:
The "poison" is actually harmless A.
The body converts A to B, also harmless.
The body converts B to C, deadly.
Once the A->B path has saturated you get an A->D path.
D blocks the B->C reaction.
B is eliminated from the body faster than D.
While I am not aware of anything with this behavior there are things that exhibit ...