Will chaos (or other problems) result from letting my players use Open5e.com instead of the WOTC collection of books?

Question

I'm DM of a group that just completed a one-year long campaign, and we are about to start anew. But my players have asked if instead of using the ever-growing list of official published WOTC books, they can instead just use all the material indexed on open5e.com, as regards all player options beyond the core rules, such as sub-classes, spells, feats, etc.

My question is, have any other DMs done this before, and did it create balance issues, or any other friction or difficulty in running a table? If you did this, then were there any caveats or adjustments you had to make to preserve continuity, integrity, consistency, or balance of the game? Are there any preparations from a DM perspective that seem necessary?

A good answer will refer to actual experience at your table as substantiation.

Answer 1

Yes, it's likely to create problems and highly likely to create chaos

Open5e.com content mainly comes from various third party publishers, the only official content on there is the basic set of core 5e rules. What you are doing is basically giving your players a blanket permission to bring in anything from a huge list of homebrew options, there are probably hundreds of ways these homebrews can create unforeseen (and problematic) interactions with one another, especially since they come from several different publishers and probably haven't been play-tested to the extent that the official content has been.

Most of the options seem to come from Kobold Press, which I have personally used at my table, they are generally considered to create good content but I have still managed to find things that were not balanced well or had the potential to break the game when combined with something else. I often use third party content in my campaigns and what I would recommend is that you either go through the content, consider each one carefully (yes, it's a lot of work if you want to cover everything) and curate a list of allowed, pre-approved options OR allow your players to pick from everything but with the explicit understanding that you reserve the right to review and potentially veto any third party content they decide to incorporate into their characters.

How exactly this will play out depends on the type of players at your table. Are they the type that tend to min-max, rules-lawyer and/or look for and exploit loopholes and corner cases? If the answer is yes, then I would tend to be conservative with third party options as there's a high risk they will find something that breaks the game balance.

Answer 2

How much do you trust your players?

You can make fundamentally broken characters using WotC rules with no 3rd party content. Doing so with 3rd party content is also possible.

If you trust your players to have both the self control and system mastery to tell that the rules they use to make their character have problems, then there really isn't an issue with using 3rd party rules for characters.

You should make it clear that any and all rules a player uses to make a character are up for discussion and modification later.

If someone makes a nuclear wizard based off of the "magic missile is one damage roll", or creates an infinite simulacrum chain, or a bunch of other frankly crazy builds, you'd have to have that conversation in a pure-WotC game.

An issue that can happen is that people who like playing around with rules are more likely to be the ones wanting to use a wider selection of rules to play around with. And if they lack self control or have a different perspective than you do, they could pick rules that cause problems at your table - be they annoying to adjudicate, overshadowing other players at the table, or out of the scope of what you want the PCs to be doing.

To prepare for such a thing:

• Have practice with homebrewing rules yourself. Not just academic knowledge, but see what happens when your rules are used.

• Get everyone on board with rulings not rules of 5e. Make it clear that you will be making on-the-fly rulings that could override the rules they used to make their character.

• Talk to each player about how they view their character. Not just the mechanics, but what do they see their character as being good at, weak at, etc. Because matching player expectations to character capabilities (and calibrating those expectations!) is more important than the exact rules used to express character capabilities.

• Do this with players you can trust. Let them know that you are relying on that trust; this can't work as an adversarial game where they try to "sneak" a rule into the game past the DM.

• Communicate to the players that the purpose of the open homebrew rules should be to take a character idea and express it mechanically. You can be inspired by mechanics to make a character idea.

If you aren't sufficiently confident with letting your players do all of this, you can instead approve things on a case by case basis. Make it clear your approval is conditional! And that players (if they plan on some combo down the line) should describe that as well to avoid possible disappointment.

Most tables I've been at allow people to propose homebrew content to be used by their character. At a number of tables I've had DMs actually ask players to try out some specific homebrew content (not even theirs) as it fit the setting/story they are doing.

D&D it not a finely tuned machine. D&D for most of its existence has had groups playing with widely divergent sets of rules and having fun; often the different rules where because they misunderstood the rules in insanely different ways! And despite that, the game can work.

The social contract is far more important than the actual specific mechanics.