Now for most games, unique magic items are more fun but can be quite limiting as a resource on their own.
But what if we want to create a castle where ALL the magic items are
cursed due to the corruption from the Necromancer Lord ravaging the
region?
In the case of Players knowing the curses are coming, they can
either simply cast 'remove curse' ahead of time or the GM needs to
prepare a big ol' list of magic item before the sessions in case they
find a treasure trove (for those of us who like rolling for treasures).
In either cases, the result is either unsatisfying for the players or
the GM. Now the GM could simply bite the bullet and prepare all those
but with our aging demographic, time is not always on our side for such
endeavours. So I tried to work at the problem and ended with a few
unsatisfactory solution. (I will conclude with the version I found most helpful so far)
the_Unique_Curse
The best thing about these handcrafted items has to do with their flavour; very rich, high impact, often high in sodium. With these you can balance them out as you choose without the constraint to rules from any system. For example:
Friendly fire
This ring casts a 2d8 fireball but can only do so if it also hits an ally.
This is an easy way to balance an item in the way of your choosing; by giving it a drawback. They are very useful to also create tension in play as the Players know the expected effect and have to consider them in their decision to use it or not.
the_Classic_Curse
The less interesting way of handling cursed items is to simply reveal an hindering effect at the time of its first use. The sword had a +3 lightning bonus? Gotcha! it was a -1 all along. Now go get that remove curse spell ready for tomorrow morning.
Not very exciting or even much lasting consequences for that matter, but it surprises the party and catch them off-guard when they did not expect it, which is often enough to make them paranoid for a bit.
the_Build_A_Curse
Every time a new item is acquired, the GM rolls on a few separate tables to generate the curse afflicting the current item: a table for the trigger of the curse, a table for the actual effect of the curse and finally a table for the duration/condition of removal of the curse.
Now I thought this was pretty close to what we needed. Easy and fast to make, a significant amount of possibility (with large enough tables), but sadly high maintenance for the GM. They would have to note what item is cursed with what set of result on their side and remember them when the PCs trigger them into effect. Plus, the effects sort of feel similar when done in this way, a generic variation of essentially the same effect you don't engage with.
the_Pocket_Curse
Now the closest answer I got to my imaginary problem so far is the following: rather than making the whole object, you have highly focused SIMPLE curse. For example:
Poet
The curse is revealed once the item has heard someone use swear words.
The accursed now must speak in rhymes
The curse is lifted after hearing a new haiku for 30 consecutive days.
This way of handling curses means the characters know there is a downside to looting artifacts in the area but makes it actionable rather than an simple penalty. The workload for a GM to prep becomes much lower as you don't need to think of the curse as part of the object itself, instead you create smaller effects as time goes and line them up or roll on a table to maximize your time prep.
All you need to do to make up a simple curse is basically a theme to center it around, a trigger that will afflict the holder of the item, a condition the player has to deal with as long as they are afflicted and finally a term of removal to end it. Of course, like in standard Old-School fashion, once the curse is triggered, you can't get rid of the item.
Spells like remove curse or detect magic should probably only reveal the name of the curse - Poet, in our example - to give sort of a heads-up to our player of what might come if they decide to keep and use it. On they other hand, identifying it should reveal its benefits so players are more interested in putting them to good use.
I think method works best when the Players know the curses are coming. It makes them careful but also add some sort of quirks to their character until they work at removing it. They might not be able to sleep anymore or have to drink blood or never take a right turn. And that creates character growth in a way most player will enjoy.