No Plan Survives Contact with the PCs

Question: Mention has been made of Folkvardr "running the triple crown" of immersion in the three magical Norse wells (Urd, Hvergelmir, and Mimir, correct?). What kind of system or guidelines do you use for the ramifications of these kinds of otherwise unquantified actions, or others such as eating the Apples of the Hesperides (or Idun)? What is a hapless Storyteller to think when a player actually pulls off the unthinkable?

I usually think, "Man, that player is awesome. I hope they're ready for some awesome consequences along with their awesome rewards."

The safest route, when it comes to big ginormous things in Scion like Urdarbrunnr or the Apples of the Hesperides, is to just have a plan ahead of time as a Storyteller; if you know your players are going to be running around the roots of Yggdrasil, you can have a plan in mind for what might happen if one of them trips over a dragon and falls into a well. But what do you do when you sit down at the table for the game and a player announces with no warning that they've decided that they need to run to the Styx for invulnerability because it's the only way to win their current struggle? It's not like you can pause the game for half an hour while you go sit down and figure out what's going to happen when he does.

Usually, we try to stick with what that magical thing, place or being does in mythology and translate it into a permanent stat effect that makes sense; just knowing a little about those kinds of things gives you a great leg up on figuring out what to do on the fly. You can keep notes on various major things you know your players are aware of (either in-game or out of game); if you have a laptop, tablet or super-phone available that you can use during game, you can also look up those mythic things quickly without having to keep much around ahead of time if you need to. Every magical item and place is different, so there's no real hard-and-fast template to use for figuring out what they do, but assigning a mechanic to something they're said to do in myth usually works admirably for us. Here are a few examples from our games:

Hvergelmir. The frozen well from which all cold water and ice in the world flow seemed like an obvious source of frostiness, so throwing himself into it gained Folkwardr several Frost boons (but lost him boons in other areas that made way for them). It also required hefty Stamina + Fortitude rolls to survive the biting cold, which Frost Immunity could not combat; had he not been an awesome roller and spent Legendary Deeds, Folkwardr might simply have ended up frozen to death in the bottom of the well instead of unconscious beside it.

Idun's Apples. Since the apples are something all the Aesir are said to need a semi-steady diet of, we ruled that they have no effect on god-level Aesir PCs; instead, they have a negative effect, in that any Aesir who fails to eat one at least once per year starts taking aging penalties to their physical stats as their immortality has not been replenished. Anyone of less than god-level Legend who eats one of Idun's apples would likely gain bonuses to Stamina and, if they didn't already have it, the Eternal Youth knack, to reflect the apples' legendary age-defying qualities, but they might also find themselves hooked and needing another "fix" from time to time to prevent these benefits from fading.

Mimisbrunnr. Two different characters have been into the well of Mimir in our games, so we're very familiar with it. The major attribute of the well is that it grants wisdom, so strongly in fact that Odin himself drank from it, so we had it grant large bonuses to Intelligence, Perception and Mystery for those who drank or immersed themselves in it as well as giving them several mental Knacks for free. Traditionally, however, it also costs a body part, so doing so automatically causes one (whichever is most appropriate for the character - something that is a serious handicap for them, no "oh, no, I lost my pinky!" here) to be taken from them at the same time. Should the body part ever be restored, the benefits of the well are lost.

The Mnemosyne. The Mnemosyne (and the Lethe, while we're at it) are famous for their effects on the minds of those who drink from them; those who drink from the Lethe forget everything about their lives, while those who drink from the Mnemosyne receive clarity of memory and vision. The rivers are, however, designed primarily for the use of dead mortals, so while they probably work as advertised on low-Legend Heroes and Demigods, it's difficult for gods who don't need them to get much use out of them. When Vala tried to toss herself into the Mnemosyne to gain further mental clarity, she rolled her Intelligence against the river; she actually rolled so high that the river turned out to not have any improvements for her, and the end result was just that she ended up damp and frustrated. Had someone with less of an acute memory succeeded in entering the river, however, they would have gained bonuses to Intelligence and Perception, but likely also penalties to their physical or social stats as their ichor, shunted into their mental faculties, compensated by being less present elsewhere.

Urdarbrunnr. This was one that Folkwardr's player surprise-sprang on the game, so it's a good example of ST feet-thinking. The well of the Norns isn't as clearly described in its effects as many others, so we had to play it by ear and get creative; as the source of the Norns themselves, we decided that it granted several boons and bonuses from the Fate purviews. Gylfaginning also says that anything put into the well becomes "as white as the skin of the inside of an eggshell", so it turned Folkwardr's skin and hair completely white as well as giving him severe Stamina and Fortitude penalties to reflect his newly eggshell-like status.

There's definitely a theme of gaining mentals above (Vala and Folkwardr: they cannot have enough mentals), but stat assignment, boon or knack gain and loss and other more general effects work the same way for something physical (the Peaches of Immortality, for example, probably give some nice physical effects in exchange for Xiwangmu hating you forever) or social (the Apples of the Hesperides might grant social bonuses in their apples of joy/bliss role). Took a dip in Manannan mac Lir's cauldron, where limbs regeneration and sickness can never be? Congratulations, you probably have some resistances to the Health purview now! And so on and so forth.

In the end, like most things Storytellers have to do, it's a combination of creativity and quick reaction time. If you aren't comfortable with your level in either, consider making some basic plans for famous landmarks or magical items ahead of time, so that if a PC suddenly goes off the rails and decides to make a run for the Ocean of Milk, you'll have an idea what's going to happen if they make it.

(Edit: John has the full notes on all these things, and the PCs in question probably remember them better than I do, so if something up there isn't quite right, mea culpa.)