How do I decide what is a "reasonable" Suggestion? [closed]

Question

I have already asked some questions that concern the Suggestion spell (here and here). However, there are still some aspects of this spell that are not clear to me. In particular, the fact that the course of action must sound reasonable can be ambiguous. According to the manual, you cannot ask a target to stab himself, but you can ask him to give his horse to a random person. Now, consider for example the following situations:

• A halfling is carrying a magical ring that could be extremely dangerous if it was in wrong hands. A wizard suggests him to give it to the first person he meets.
• A young seaman has just been given a giant vessel and he is going to set sail, the dream of his life. A wizard suggests him to sell him the vessel for a few money.

can the Suggestion spell be used in these situations? Can these courses of action be considered as reasonable? In general, how to quickly determine if the course of action is reasonable?

Answer 1

This is ultimately subjective and up to DM ruling, but if you want a quick way to judge it, imagine that "Suggestion" is the name of a bottle of strong spirits, you just drank the whole thing, and now it's telling you that doing X would be totally awesome.

Ten years from now, will you be in the bar with your fellows, saying "Haha, remember that time when I drank a bottle of Suggestion and then X!"? That means it was totally reasonable, so X goes.

On the other hand, ten years from now, will you be waking up crying in the middle of the night, shouting "Why, why did I do X!"? That means it's not reasonable, so X doesn't go.

This would make giving away The One Ring very unreasonable, but giving away the magic ring you just "liberated" from some "evil creature" totally reasonable. It mostly makes it so the reasonable-ness of any act is judged by how much it's going to ruin your life and haunt you, not by any amount of monetary value or whatever, which seems to be the idea behind the spell.

For example, you might get a noble to give you his purse of gold, but not get a farmer to give you his only cow. You could, however, convince the farmer to dance naked through the streets, but you couldn't convince the uptight noble to do the same.

Answer 2

Rules as written, there is almost no guidance about Suggestion. The spell's power level is all a spot-ruling by the DM. There is no clarification anywhere in the book about what reasonable means

The Suggestion spell is extremely vague at what it can and cannot do, and Wizards (through Sage advice and tweets) have been very cagey about trying to nail it down. There are no officially published explanations for exactly how far the Suggestion spell can go. Even the example given in the book (Convince a knight to give her horse to the first beggar she meets) is unclear, as we don't know anything about the knight or the situation or the outcome. Is she currently on a quest? Does she have multiple horses? Is she in the middle of the desert 100 miles from the nearest town, meaning that giving up her horse is suicide? Is it her favorite horse? Is the horse a polymorphed version of her best friend that she's trying to cure? What happens once she gives up the horse, does she just walk away? Does she give it away and then immediately take it back? Can she ever take it back? What happens if the beggar tries to sell it to her? Does she still want it? Would she pay more or less for it? Does she even still recognize that it's her horse?

5e's mantra is 'rulings, not rules', and the Suggestion spell is the perfect example of this. It's simply not possible to know what the spell is capable of without having a conversation with your DM before you start the game. The DM will also likely break this ruling sometime during the game when it becomes obvious that you've found a way to use the spell that they didn't intend, so make sure you discuss exactly what you want to do with it before you devote time and resources to a plan that hinges on the Suggestion spell. Keep in mind also that the spell will likely have wildly different power levels from DM to DM and game to game. I've played in games where Suggestion was a social I-Win button and the very next game it was worse than a persuasion check.

There are lots of interesting theories and house rules and 'here's-what-reasonable-REALLY-means' out there on the internet that you can read for yourself, but the actual answer to your questions of 'How does Suggestion work with':

• A halfling is carrying a magical ring that could be extremely dangerous if it was in wrong hands. A wizard suggests him to give it to the first person he meets.
• A young seaman has just been given a giant vessel and he is going to set sail, the dream of his life. A wizard suggests him to sell him the vessel for a few money.

Is that there is nothing in the book that can give you a concrete answer. These will depend 100% on the DM, and in fact the answer will probably be different each time you try.