D&D 5E Magic Items found during the game: How do you handle the "oh look, this random dungeon just happens to have that sword my character wanted."

[Clancey]

OK, from a player standpoint (because it has been 30 years since I've DM'd or played until recently) I have had to fight a being who used the item on me and defeated him, which is very satisfactory and a way to explain why I know at least some of its properties. I also would like to find items which have a reason for being there. Example - Giant Slayer weapon found in the Against the Giant's campaign. It was brought in by a dwarf who was defeated by the giants (no, it wasn't in the module, but it could have been) who never threw it out. You know, something that makes some sort of internal sense. Random generation is all well and good, but most magic items found by my parties have been potions or scrolls, or bag of devouring, shield of Arrow attraction or cursed armor or only useful to an npc. Very little straight-out great items. The bag of devouring is probably the rarest item we've found to date. I don't think our dm would ever throw in a taylor-made magic item, and I'm not too sure I would want him to.

 

[The Crimson Binome]

In 4e or 5e though, most NPCs don't use Feats, they have abilities assigned by the GM. NPCs may well
have particular abilities with certain weapons, abilities that are not in the PHB.

In 5E, feats are an aberration. The default game assumes that feats don't exist. If you change the game by bringing in feats, then the world changes to reflect that. Thus, an NPC that would otherwise have chosen a particular feat if it had been a PC, might gain some of the simpler mechanical benefits of those feats. Remember, the only reason why NPCs have simpler stats is in order to aid bookkeeping; if we can add more accuracy, without increasing complexity to an unreasonable degree, then we should​.

In a no feat game, humans can't see in the dark, so a human assassin NPC can't see in the dark. In a feat game, anyone taking the super sneaky assassin feat can see in the dark, so a human assassin NPC (of sufficiently-high effective level) should gain darkvision to reflect that.

 

[Connorsrpg]

Wow. I would probably have a bunch of 'grumpy' players in my games...except that I never have. Treasure is usually random, and oddball items have changed the directions of characters in the past. And led to some fantastic encounters too.

However, since 4E I have had an option on the PC Pages of my websites for players to put a little 'Wishlist'. Most players have ignored it and are just happy to receive anything in my games But, to integrate some ideas I have gone with what others have suggested, namely lore and adventure hooks. (Even changing the bad guy's weapon to one the players wanted). OR had the weapon magically (usually with divine intervention) actually become magic (or increase). Rather than just have stories of how weapons wielded by great heroes now contain great magic, I have actually allowed that to happen with the heroes of the day.

 

[Lord Xcapobl]

Not that they are the best weapon for every situation, mind, but the distribution of magical weapons throughout the world should reflect the set of weapons that are actually used.

In a way, this can also refer to regions and cultures. You play a character from Waterdeep, but you want to have a Katana +1? Make a trip. A long one. Be prepared to travel all the way east into Kara-Tur. Did you build a Kopesh-Master from the Dale Lands? Fine. But seeing as to how the kopesh is a weapon based on ancient Egypt, and, in the Realms at least, Milhorand seems to be its equivalent for ancient Egypt, make a trip. A long one. Probably not so long a trip as in my katana example, but from the west to the east side of the most used Faerun map anyways.

In my homebrew campaign, this is also a factor. Some weapons are linked to certain cultures, and as such, the biggest chance to find a magical version is by going into the territory where that culture is prevailent. If you are raiding tombs in a region loosely based on Western Europe, you find swords, spears, axes and bows, not katanas, naginatas, sianghams, jambyas, kopeshi and whatnot.