Sure, but you said there is no benefit without a penalty. That is an extreme position.
when I DM the goal is not for me to drop the hp number to zero. I want to challenge them, of course, that is part of the goal of running the game. However, challenging them is not the same as defeating them. And I don't see the value in approaching the game with the mindset of defeating the players. IF that's all I'm supposed to do, it is child's play.
War vs sport again, only in a larger context than just combat.
If you're going to go out adventuring, you're willingly putting yourself into situations where the game world is out to kill you; and will, if you're unlucky or foolish or pick the wrong challenges to take on. It's not sport, it's war. Thus, survival is goal number one.
So, picking up none of these items is harmful.
Damn - I knew I got something wrong there; one of them (the silver rod?) was supposed to be harmful on touch.
And basically any group I am running with has the Identify ritual ready to go to tell us all of this information. That's what Identify does. You can also identify what a magic item does during a short rest (we sometimes roll arcana).
Another example of 5e making things (too) easy on its players/PCs.
Therefore the party will ditch the boots. They are utterly worthless and actively harmful.
Indeed; they're a not-quite-death trap. Not quite death, in that the PC is technically still alive and can still think etc., but not exactly conducive to a continued career in adventuring either.
Maybe they keep them if they think they can use them as a deathtrap for someone they don't like.
The rod they keep in a backpack and probably forget about, unless there are metallic dragons they need to talk to.
The Gem is interesting. Someone is probably willing to take the risk, though we are going to ask how easy it is to remove. You personally won't tell us, but the asking is to measure the risk. If this ends up being "you die if hit with a critical hit" that is very different than "someone has to pin you, and forcibly rip it out of your skull" in terms of the risk associated with it.
I've actually had these gems in my game for ages, with a wide variety of powers and abilities, and there's a small body of knowledge built up around them which PCs would be able to learn with a bit of inquiry.
Removing one outright is a Very Bad Idea, and probably can't even be done without violence - i.e. literally prying it out with a crowbar - as it's fused to the wearer's skull. There's a way of replacing one gem with another, at some risk.
Dispel Magic, if it manages to knock out the gem's enchantment (low odds at best), is deadly. If the wearer fails a save vs AoE damage, having the gem fail a save vs destruction is Bad (but its saves are pretty good).
These gems are usually very powerful, though; and thus arte high-risk high-reward items.
Someone would then wear the rope. And they would probably end up saving the ring for a useful wish.
The point of the wish ring is that there's no way of learning what it does without wearing it, and as soon as someone puts it on its effect takes place after which it's a bland gold ring.
The vial is weird though. And leads me to my question... what's the point of some of this?
Deception. Trickery. Chaos. High risk, high reward.
Why have a potion that seems like giant strength but is actually a decent healing potion? The healing is a fine reward, and this runs the risk of them drinking it at full health, expecting a strength boost and instead wasting it because they were full health. It seems like an item literally designed to be wasted because the players are being deceived. What is the actual goal with that?
It'd be a variant on the old Potion of Delusion, which makes you think it's a real potion but in fact Does Nothing. Here, it just does something different; still beneficial, but not what you're expecting.
The boots are even worse, if you don't allow identify or anyway to figure out what they do. Because a player who puts them on to find out what they do dies.
Ayup. And there's loads of precedent for such items, the Necklace of Strangulation being one such.
And, acting with no knowledge and being forced to guess, while guessing can get you killed, isn't a fun game. You might as well roll a die everytime someone declares an action, and kill them on a 1, because that is the same amount of control the players have.
There's a strong element of luck in the game, to be sure; and that's part of the point. If the game wasn't built around luck, it wouldn't use dice.
Now, depending on level and resources the boots might not be an outright death trap.
Augury and-or
Portent can really help here, as can a Bard's Item Knowledge ability (or maybe even Legend Lore); and
Commune and other divinations at higher levels.
This doesn't surprise me given your list of magical items. Since looking at it could be an instant death sentence in your games.
Personally, I've found that since I don't arbitrarily kill PCs with no warning, they tend not to act like every single item they interact with could be instant death. And when it would be... I pretty much just tell them how deadly the item is. (And some of them still touch it, but I told them, so there aren't any hard feelings)
Sometimes there's warning, other times not, depending on the situation.
But even warnings can be misinterpreted. Say the party enters a room; and on the floor of the room is a skeleton, posed as if reaching for a sword* on the floor close by it. Now, was the dying person reaching for the sword because the sword could save her, or did the sword kill her and just happen to fall there when she collapsed?
* - the sword's grip is trapped with a deadly-poison needle.