For Ring of Spell Storing, when does Wild Magic Surge trigger?

Question

If a Wild Magic Sorcerer stores a spell in the Ring of Spell Storing, when can the DM ask for that player to roll a d20 to determine if a Wild Magic Surge triggers? Is it at the first casting of the spell, when it is stored, or at the second casting, when it is released?

Here is the text for it:

Ring of Spell Storing

[...] Any creature can cast a spell of 1st through 5th level into the ring by touching the ring as the spell is cast. The spell has no effect, other than to be stored in the ring. [...] The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell.

Answer 1

Based on the wording there, I would be inclined to say that it cannot wild surge when cast from storage unless the wild mage is also the one casting it from storage.

The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell

This doesn't mention wild magic as one of the things that's retained from the original caster, so if someone other than the wild mage used the spell there would be no surge. If the wild mage is the one to use the stored spell, since it is treated as them casting the spell for everything not explicitly listed, I'd say there's a chance for a surge.

As for storing the spell, it says that the spell has no effect, but the description of the Wild Magic Surge feature says

Immediately after you cast a sorcerer spell of 1st level or higher, the DM can have you roll a d20. If you roll a 1, roll on the Wild Magic Surge table to create a random magical effect.

This strongly suggests that the wild magic effect is not part of the spell itself, as it happens after your cast the spell. In particular, no wild surge effect modifies the spell that triggered it. So it seems fair to say that storing the spell can trigger a surge.

Answer 2

It can be either, or both

The DM can call for the Surge, or not call for it, at DM discretion.

"Both" is a well supported ruling.

Wild Magic Surge says (PHB p. 103)

... your spell casting can unleash surges of untamed magic. Immediately after you cast a sorcerer spell ... the DM can have you roll a d20.

From the Ring of Spell Storing text

This ring stores spells cast into it ...

While wearing this ring, you can cast any spell stored in it.

Whenever there is "casting" by the Wild Magic Sorcerer, for spell of level 1 or higher, the DM can call for that roll.

Can versus must

There is no rule that the DM must call for the Wild Magic roll, the DM can. This is a complaint some people have with this sub class of Sorcerer, that this class feature is subject to a DM ruling each time a die roll may be called for.

Since it isn't a hard and fast rule -- if this, then that -- the true but unsatisfying answer to your question is "if the DM prefers before and after, so be it. If the DM prefers before, so be it. If the DM prefers after, so be it."

Why "cast from ring" makes good sense if you only want one trigger

The Sorcerer can cast from the ring regardless of who loaded the ring. If another sorcerer, or another caster, filled the ring, the sorcerer with the ring doesn't cast it (and would not trigger the effect) until casting from the ring. If what you'd like is to keep it simple at your table -- KISS principle -- triggering the roll chance when the spell is cast from the ring makes sense.

Crazy Fun Method

If you are in a low combat / high non-combat encounter mode, there is room for a lot of hilarity/fear with this feature. If, for example, while the sorcerer is filling the ring (say, at a tavern) a wild magic surge goes off, blows up the room (or what ever) it can add to the RP and interaction with the town.

• Crazy Fun example from @Xavon_Wrentaile

  The Surge happens when the ring is charged, but goes into the ring as part of the spell, and is not noticed until the spell is released.

What would your players prefer? Talk to them. Some groups like random stuff like that. Some don't.

Rule of cool/Rules as Fun

If you are the DM,

• when do you want it to trigger a chance at wild magic?

• When do you NOT want to trigger that chance?

That's up to the DM, but I'd recommend working with your player on getting the feel right for your table.