I’ve been working on interesting, unusual circumstances and situations to help teach my two new players about the different mechanics in D&D.  I want to include poisons and diseases in this project, but one of my veteran players is playing a paladin.  He can just nullify diseases and poisons with his Lay On Hands, so even if I infect/poison the entire party, it’ll only take one long rest to heal them all up (it’s a party of five, at fourth level).  It doesn’t seem fair to invent an effect that’s specifically immune to paladins.  Has anyone found a fair way to circumvent a paladin?

A fair way to circumvent Paladin abilities?  No, not at all.  It begs the question, why would you want to?  It seems like a perfect way to show your new players why poisons and diseases are not the great terrors they are in the real world, why Paladins seem heroic, and why clerical magic in general is highly prized.

Lesser Restoration also makes disease irrelevant, so the reality is that 5e wanted disease to be mostly a nonissue for PCs.

It’s not that I want to permanently make his abilities useless.  I’m just working my way through the various mechanics of the game, creating situations to teach my new players how D&D works.  I want them to be at least familiar with what they could be up against, in case the paladin ever has to miss a session; they rely on him pretty heavily to fix them up, without even thinking about the fact that there might be alternatives.  I worry that if he ever has to be absent, they’ll be paralyzed with fear, since he’s their safety net.

Maybe I’m going at this with the wrong mindset, but I can’t help worrying.  Is there a better way for me to do it?

Disease comes up so rarely. It’s nice to let the pally actually do his thing and cure it.

And the lesson to the new players can be, paladins are awesome.

Okay.  I’ll try.  *sigh*

I was not prepared for how much DMing feels like parenting!

Honestly, there are far more "lessons" to teach new players than diseases and poisons. Diseases tend to be longer term. Most poisons (at least from monsters) are of limited duration. Neither are usually all that common or important in most campaigns unless the campaign or adventure has been built around the party having to cure a specific disease affecting a local population.

More important things are ...

- attack rolls

- saving throws

- ability checks

- roleplaying

- significance of ability scores

- race/class abilities

- significance of armor class and heavy/medium/light armor + shields

- three pillars - combat, exploration, social interactions

- npcs

For earning to play D&D - diseases and poisons are almost insignificant (at least in my opinion :) ).

P.S. Inflicting a disease or poison on the party and then having the paladin and whoever can cast lesser restoration working together to cure it should be all they need to learn about it. As long as someone else besides the paladin can cast lesser restoration - the party will have a way to deal with it if it ever comes up. (You could also have them seek out NPC healing if they need it to get an idea of interacting with the world)

I keep thinking about this.  You said that you had 5 players, at 4th level.  That's the Paladin, the two new players, and two others.  What are they?  The Lesser Restoration spell can be cast by a Bard, Cleric, Druid, Ranger, Artificer, or the Variant Aasimar from out of the DMG, who can do it once per day.  It makes perfect sense that no warrior types would be able to cast Lesser Restoration, but Rangers, and Artificers can.  It makes perfect sense that no Mage types can.  There are 13 official classes, 8 of them cannot cast Lesser Restoration somehow, so with 4 players, none of them are playing a Bard, Cleric, Druid, Ranger or Artificer?

We already established that an Herbalism Kit can be used to create an Antitoxin, so poison is pretty trivial.  Disease proves to be pretty trivial too, even if your entire game is based around disease, I think your two new players are pretty safe.  There's nobody that cannot cast Lesser Restoration at least once per day.

Sometimes the choice is between curing wounds and curing poison. 

Or split up your PCs and have them race to find the paladin before they succumb to the disease? 
Probably not for everyone, but I could see it working with the right group.

Aside from the paladin, we have an evocation wizard and an archfey warlock (the two new players), a monster hunter fighter, and an artillerist artificer (no Aasimars).  I wasn’t aware that artificers could cast Lesser Restoration; that helps with my nervousness.  The warlock is proficient with the herbalism kit, although I keep having to remind her about it, and what she can use it for.  I also gave them a one-way, one-use teleportation scroll that will transport the party to one of the main temples in my world, with a promise of healing from the priests there.

They’re pretty good with the basic mechanics.  Lately I’ve been branching out to things like cover, stealth/hiding, conditions such as prone, unconscious, etc., climbing/swimming, investigation and perception, and so on.  My goal is to introduce these now, while the stakes are relatively low, so that later in the campaign I can use them without worrying that the new players might be caught unawares by something basic.

I’ll just let the paladin cure the poisons/diseases.  It seems I worked myself up over something minor!

Edited to add: I have yet to figure out how to teach roleplay, however.  It comes naturally to me, so I don’t know how to help others learn.  Mostly I try to reward it when I see it, with advantage or inspiration, as the situation warrants.

It is very hard to teach roleplaying.  The best I can think is to talk about how it's like improvisational theater.  In a play, the DM does most of the work, the players are like the actors.  They make up their lines to fit the script.  This was something Robin Williams was infamous for in movies, and look how much fun "Aladdin" turned out to be.  He made a career of being very silly, and it was very funny, but even in a serious toned movie, it remains true.  In the original movie Blade Runner, Rutger Hauer's ending speech, the one that starts with "I've seen things that you people wouldn't believe..." was pretty much impov.  He was supposed to do a much longer speech, but he took the basic ideas and made up something that he liked better and the director kept it.

If you want effect that can affect the PCs without being poison or disease, i suggest madness effect in the DMG.

Quote from HazelSage >>

It’s not that I want to permanently make his abilities useless.  I’m just working my way through the various mechanics of the game, creating situations to teach my new players how D&D works.  I want them to be at least familiar with what they could be up against, in case the paladin ever has to miss a session; they rely on him pretty heavily to fix them up, without even thinking about the fact that there might be alternatives.  I worry that if he ever has to be absent, they’ll be paralyzed with fear, since he’s their safety net.

Maybe I’m going at this with the wrong mindset, but I can’t help worrying.  Is there a better way for me to do it?

I think a situation where one or more characters get poisoned or something worse for part of the encounter will give them a decent sense of how dangerous/serious poisons and diseases can be, even if the paladin then heals it to avoid any long-term effects

Alternatively, if it's the "what will they do without their binkie?" issue that worries you, you could create a scenario that separates the party temporarily/isolates the paladin, so that everyone else has to find a way to deal with conditions that he could otherwise take care of. Even something as simple as a rockfall in a cave or dungeon, trapping the paladin on one side so that they have to find a way around to meet back up, might do the trick

Quote from Geann >>

It is very hard to teach roleplaying.  The best I can think is to talk about how it's like improvisational theater.  In a play, the DM does most of the work, the players are like the actors.  They make up their lines to fit the script.  This was something Robin Williams was infamous for in movies, and look how much fun "Aladdin" turned out to be.  He made a career of being very silly, and it was very funny, but even in a serious toned movie, it remains true.  In the original movie Blade Runner, Rutger Hauer's ending speech, the one that starts with "I've seen things that you people wouldn't believe..." was pretty much impov.  He was supposed to do a much longer speech, but he took the basic ideas and made up something that he liked better and the director kept it.

 I actually spent most of my childhood/teenhood in community theatre, and improv was always my favorite subject!  I was pretty good at it, too, if I do say so myself. ;)  It didn’t really surprise anybody when I became a DM.

Quote from AntonSirius >>

Quote from HazelSage >>

It’s not that I want to permanently make his abilities useless.  I’m just working my way through the various mechanics of the game, creating situations to teach my new players how D&D works.  I want them to be at least familiar with what they could be up against, in case the paladin ever has to miss a session; they rely on him pretty heavily to fix them up, without even thinking about the fact that there might be alternatives.  I worry that if he ever has to be absent, they’ll be paralyzed with fear, since he’s their safety net.

Maybe I’m going at this with the wrong mindset, but I can’t help worrying.  Is there a better way for me to do it?

 

I think a situation where one or more characters get poisoned or something worse for part of the encounter will give them a decent sense of how dangerous/serious poisons and diseases can be, even if the paladin then heals it to avoid any long-term effects

Alternatively, if it's the "what will they do without their binkie?" issue that worries you, you could create a scenario that separates the party temporarily/isolates the paladin, so that everyone else has to find a way to deal with conditions that he could otherwise take care of. Even something as simple as a rockfall in a cave or dungeon, trapping the paladin on one side so that they have to find a way around to meet back up, might do the trick

 This party splits up fairly regularly, although I haven’t taken advantage of it yet.  I’ve been thinking about how to try this technique in our game tomorrow.  It’s their first real dungeon crawl!  It’s fairly short, but there are a few opportunities.  We’ll have to see how tomorrow goes.

Well, you could always not tell them outright that they have contracted a disease.

Determine when they became afflicted and then start slowly giving them symptoms. One of three things will happen:

1. Pally goes around the group and neutralizes the disease as soon as strange symptoms start with a batch of "just in case" Lay on Hands uses.
2. Detect Poison and Disease gets cast prior to option 1.
3. The effects get worse until someone thinks "maybe I should do option 1."

In any of these cases you're not circumventing the Paladin's abilities and, in fact, you are letting them shine by giving them an option to make use of a rarely used option for one of their features.

Edit: Or you could be a butt and wait until the pally has used all, or most, of his Lay on Hands points.  :P

Poison and diseased conditions are relevant in combat, and paladin has to spend a full action to heal one of them. If you want to make them being important, infect the party in combat. Let them role play their conditions. Then paladin has to decide if they want to heal their friends or fight monsters. Good opportunities for character development and bounding within the party.

"Diseased" is not an officially listed Condition.  Poisoned is, yes.  All the diseases in the Dungeon Master's Guide have an incubation period measured in hours or days.  The symptoms can be somewhat serious, but it's entirely irrelevant in combat unless you are fighting for at least an hour continuously.

Quote from Geann >>

"Diseased" is not an officially listed Condition.  Poisoned is, yes.  All the diseases in the Dungeon Master's Guide have an incubation period measured in hours or days.

 Contagion takes 3-5 rounds to take effect. Aboleth slime isn't directly combat relevant but you only have a minute before it becomes highly problematic. It's rare for disease to be relevant on a combat time scale, but it can happen.

Quote from GoodBovine >>

Or split up your PCs and have them race to find the paladin before they succumb to the disease? 
Probably not for everyone, but I could see it working with the right group.

 Splitting up the party is the old DM go to for the party that has an answer to everything. Most players, consciously or not, build their characters and groups to cover all the bases. A good story involving 2 or more smaller groups of all the characters is more work to DM but, could evoke outside of the box thinking.