Free feets!

[Aaedimus]

I give my players a little glowy gem. As long as it's on their person, they have access to a feat they wouldn't otherwise have access to.

1.) How much of a mistake would it be to let them choose the feat?

2.) Should I make the stones non-interchangeable? (To keep them from making one player uber strong)

3.) Should they need to attune? (If they don't, someone could steal the stone and use it against them immediately)

The stones will eventually be stolen from them. It's a temporary power boost (it should feel like a big thing)

4.) I thought adding some other boons would be nice. Possibly held spells, special abilities. What are some really fun abilities that might make the players feel powerful without being to complicated for them to bother with?

Ex: once a day create the effect of a bag of holding being set in a portable hole at any points you can see within 60 ft. Exclude any number of creatures of your choice from being drawn in. (Remember, in 5e it's only a 10ft radious)

5.) Should there be any negative effects to using the stones? What kind?

[MaxWilson]

The power boost is approximately the same as a Transmuter's Stone (can grant proficiency in Con saves), which is a 6th level wizard feature. It's a reasonably hefty boost, although it won't be game-breaking because any feat they get now is just a preview of what they'd get anyway in a few levels.

Seems like a fine idea to me.

For the sake of discovery and fun (not really game balance), I'd say:

No, the stones should not be interchangeable or player-selectable per se. Instead, make a certain number of stones available, and each one is tied to a given feat, and they have some way of choosing which stone they use. (Maybe the current owner of the stones needs them to do a job or something, and loans them the stones to help them accomplish it.) That adds some scarcity to the economy and gives them more affordances to play with. For reasons of game fiction, it's probably most fun to make the stones require attunement, because then you can narrate some fiction about how knowledge seeps into their minds, or long-dead spirits whisper in their ears, or whatever it is that grants them this feature.

$.02.

Edit: RE: negative effects to using the stones, I'd say yes, that can make it more fun, even if there are no negative mechanical effects. From past experience I'd say players may have lots of fun if you give them psychological flaws with no disadvantages, from the original possessor's of the stones' talents: maybe the Skulker stone makes you feel more greedy, and the GWM one gives you a short temper, and the Mobile one makes you cowardly, or whatever. Let the players know it's still up to them what they do about these feelings, but they may have a lot of fun having a virtual permission slip from the DM to display negative character traits like greed or cowardice or something without other players looking down on them for it. ("Flauntiir says I should steal the gold and hide it somewhere... and I can't resist, I do it!")

[Hecuba]

I give my players a little glowy gem. As long as it's on their person, they have access to a feat they wouldn't otherwise have access to.

1.) How much of a mistake would it be to let them choose the feat?

2.) Should I make the stones non-interchangeable? (To keep them from making one player uber strong)

3.) Should they need to attune? (If they don't, someone could steal the stone and use it against them immediately)

The stones will eventually be stolen from them. It's a temporary power boost (it should feel like a big thing)

4.) I thought adding some other boons would be nice. Possibly held spells, special abilities. What are some really fun abilities that might make the players feel powerful without being to complicated for them to bother with?

Ex: once a day create the effect of a bag of holding being set in a portable hole at any points you can see within 60 ft. Exclude any number of creatures of your choice from being drawn in. (Remember, in 5e it's only a 10ft radious)

5.) Should there be any negative effects to using the stones? What kind?



That depends on the extent to which they are interested in optimizing, better at it than you, and indifferent to the effects on the the other people at the table. Absent a situation where all 3 of those elements are in play, I tend not to be overly concerned about facilitating something a player wants, within reason.
If you make them require attunement, this largely solves itself - the person they try to stack them on would not be able to attune to other things.
Yes, unless there is a compelling reason not to.
The example seems like a fairly pronounced 1/day auto-win for most encounters. After all, you don't need to clear all the enemies before the outcome of an encounter becomes more or less assured: one or two of the strongest is usually enough. That makes this significantly stronger than a feat.
Thematic role-playing flaws are always a classic. Stone makes your reflexes faster? You become impatient and/or easily startled. Stone gives you increased HP (toughness) in the form of becoming somewhat stonelike? Your emotions and physical sensations become increasingly muted as you use it.

[ATHATH]

Where are the new feet going to go? On their elbows? On their foreheads?

[Vorpalchicken]

Where are the new feet going to go? On their elbows? On their foreheads?
Their hands are replaced with feet. If they're lucky they'll get just one hand replaced and get a +1 to one ability score.

[SociopathFriend]

Do they still need requirements for the feat like, say, Heavy Armor Proficiency in order to get Heavy Armor Master?

A giant chunk of any plausible problems is solved right there if you still enforce that.

As for picking- that depends on how nice you want to be. I'd say roll for it and so long as it's not an entirely useless feat for them give it to them like that.

Personally I love the idea of them swapping stones in the middle of battle in order to get the right person with the right feat. Xiaolin Showdown-style.

[MilkmanDanimal]

They're basically Ioun Stones that give feats instead of +1s to various scores; seems fine, but I'd definitely require attunement for those, as they're really pretty darn handy and there should be some cost. As for once-a-day abilities or something, make it interesting. Have them roll a d20. On a 6-15, they get the desired effect. On a 1-5? You've got a table for that, and use the Wild Magic surge table as a guide.

[Connington]

This might be unpopular opinion, but I think it's really OP that humans get two free feets.

[Willie the Duck]

This might be unpopular opinion, but I think it's really OP that humans get two free feets.

That's why you need to include caltrop-using opponents in your game, so that the players will learn de agony of de feet.

[Laserlight]

This might be unpopular opinion, but I think it's really OP that humans get two free feets.

You want to talk about OP, centaurs get FOUR feets.

I would give the stones a psychological flaw, which gets worse over time. See how long the players decide to cling to their stones.

[niklinna]

If you plan on having these be temporary, keep in mind how much players like having things taken from them (answer: not at all). If you have a precedent in your game for items coming and going, then fine, otherwise I hope you will clearly telegraph the temporary nature of this gift.

Maybe the PCs are explicitly told they are a gift, or that they are to be delivered to somebody but can use them in the meantime, or that they are guarding them from so-and-so who will stop at nothing to get them (thereby making it kind of expected when so-and-so gets them). Maybe they have limited uses and their glow fades over time, then having them stolen wouldn't be such a loss, especially if they are on their last legs.

[niklinna]

This might be unpopular opinion, but I think it's really OP that humans get two free feets.

All races have two free feets. Except maybe certain yuan-ti.

[Vogie]

I would give the stones a psychological flaw, which gets worse over time. See how long the players decide to cling to their stones.

I really like this. Maybe the more they use the stone, the more they're dependent on it, but then over time it becomes less and less useful, but the PC is frantic to use it first.

The Mobile Featstone makes them incredibly fast, and can dart in and out of combat... but if you use it too much, they start to realize that it's just as effective as making them run away from combat altogether. They can fight it, but at some point they'll go and leave their party behind.

[sithlordnergal]

I give my players a little glowy gem. As long as it's on their person, they have access to a feat they wouldn't otherwise have access to.

1.) How much of a mistake would it be to let them choose the feat?

2.) Should I make the stones non-interchangeable? (To keep them from making one player uber strong)

3.) Should they need to attune? (If they don't, someone could steal the stone and use it against them immediately)

The stones will eventually be stolen from them. It's a temporary power boost (it should feel like a big thing)

4.) I thought adding some other boons would be nice. Possibly held spells, special abilities. What are some really fun abilities that might make the players feel powerful without being to complicated for them to bother with?

Ex: once a day create the effect of a bag of holding being set in a portable hole at any points you can see within 60 ft. Exclude any number of creatures of your choice from being drawn in. (Remember, in 5e it's only a 10ft radious)

5.) Should there be any negative effects to using the stones? What kind?

1) I wouldn't call it a mistake, but choosing the feat beforehand can add some depth to the world. For example, the renowned Elven Sage could carry a gem that grants the Prodigy or Skilled feat, or the Orc leader of a warband could have a stone that grants Inspiring Leader.

3) I would make these gems require attunement, unless it grants one of the feats that give you armor proficiency or the Weapon Master feat. Having an attunement requirement will still make the stones usable, but it prevents them from becoming too powerful. While you do get to decide what items the players get, DMs sometimes make mistakes. And woe be to the DM who hands out a magic staff that can add 1d6 to any strike with an item that grants Polearm Master for free.

2) This is actually covered if you make the items require attunement and choose the feat beforehand. The gems are still technically interchangeable, but if they require attunement and give specific feats the party will generally give them to whoever can use them the best.

4) I don't think these items will need any additional effects. A free feat is strong as it is, its why Variant Humans are so powerful.

5) I'd say no. Generally, only cursed items have negative effects for the user. There are some exceptions to this, -cough-DeckOfManyThings-cough-, but they tend to be the exception, not the rule.