I've been reading into using Fate Core for an upcoming campaign and notice that when invoking aspects it's almost always for the best to take the +2 modifier over the reroll unless the roll is especially bad.

If I instituted a house roll to instead allow a player to reroll any number of their dice when invoking an apect would it upset the balance of the game overmuch? As far as I can tell it would maintain a level of risk as you could roll the same or worse (assuming the original dice wasn't a -) but means you could "bank" any rolled successes, however I am concerened that it would swing the balance too far in the other direction where it almost always makes sense to reroll instead of take the +2 bonus.

  • \$\begingroup\$ This question seems to imply that there's a problem with infrequent uses of the reroll option, since the house rule's purpose is to make rerolls more common. Could you explain what the perceived problem with infrequent rerolls is? It may be relevant to answering your question well. \$\endgroup\$ – SevenSidedDie Apr 7 '17 at 15:34
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    \$\begingroup\$ The main reason I was considering a houserule was because rolling dice is, well, fun! I'd rather incentivise my players to roll dice for greater risk or reward than take the sure thing every time. I also would prefer checks to be a little less mechanical in so much as currently it seems players would see a challenge and immediately consider how many aspects are needed to be invoked instead of actually roleplaying. I think that if they have the chance of better rewards they'd be more likely to try aspects one at a time and narrate the outcome of each before trying another. \$\endgroup\$ – Psycrow Apr 8 '17 at 10:02
  • \$\begingroup\$ You'd only make a partial re-roll if the number was middling anyway. So then why not just +2 and be done with it? \$\endgroup\$ – Whothehellisthat Jul 19 '17 at 19:11

As this calculation shows, re-rolling in this manner provides a mean advantage of +0.64 points. Still much less than the +2 offered by the vanilla invoke but only slightly larger than the +0.2 of the raw reroll.

So the choice between +2 and reroll stays pretty much the same. It is worth it only if you roll -3 or less.

But your approach offers a fun and interesting tactical question: Do I reroll zeros? That choice alters the distribution (but not the mean) of the results and lets you adjust your risk. You have nothing to lose by rerolling minuses, but rerolling zeros brings in equal probability of gain and loss. Just that, I think is worth exploring.

However, IMO having a big fat +2 overshadowing this would keep it the fringe choice as with the raw reroll, so my recommendation for your house rule would be to remove the +2 choice altogether or at least nerf it down to +1 so that your proposed reroll becomes the better choice for a wider range of results.

  • \$\begingroup\$ I'm trying to understand your AnyDice graph, and something isn't making a lot of sense to me. It looks like it's comparing the 4DF roll to 0 or -1, when it should be comparing each individual die against 0 or -1. You say that "It is worth it only if you roll -3 or less", but in this system, rolling a -2 (+, -, -, -) would still get a bigger bonus from rerolling the -s rather than getting a straight +2. \$\endgroup\$ – DuckTapeAl Apr 8 '17 at 20:20
  • \$\begingroup\$ @DuckTapeAl, I'm exploiting Anydice's type casting behavior. When you call a function that accepts a number with dice instead, the function gets executed separately for every possible outcome, and the results are collected. Maybe that's what looks confusing. \$\endgroup\$ – edgerunner Apr 8 '17 at 21:22

With your houserule, re-rolling would happen much more often.

I'd like to talk about the statistics of rolling a little bit before talking about balance directly. On average, a Fate die gives +0, since there's an equal chance to get +, -, or 0. If you allow a player to only reroll some of their dice when invoking an aspect, then you effectively give them +1 for every - they rolled, on average, while also giving a chance to get +0 (by getting another -) or +2 (by getting a +).

Statistically speaking, this doesn't change the numbers very much. If there are 2 -s, then it's equally good to get a +2 as it is to reroll those -s. If there are 3 -s, then it's better to reroll either with your houserule or without it. However, since this houserule gives the players a fairly significant chance to increase their roll by +2 per - they reroll, I would expect players to do this much more often than they choose to reroll in normal Fate. It's been my experience in several different systems that if you give a player the ability to have a decent chance at turning a negative into a positive, they'll take it. Also, rolling dice is fun for many people, and this houserule makes it statistically valuable to reroll in many more circumstances.

I would expect that, for most players, the default use of an invoked aspect would be to reroll any roll with at least 2 -s, rather than getting the +2 directly. Players would only take the +2 if there was 1 or 0 -s in their roll, or if they generally felt unlucky and didn't want to chance another roll.


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