Does Fiery Torrent check one or all players' prepped spells?

Name

Does Fiery Torrent check one or all players' prepped spells?

Details

When casting Fiery Torrent (Deal 2 damage. Deal 2 additional damage for each Fiery Torrent prepped by any player), additional damage is dealt for any other Fiery Torrent prepped by any number of players.

This is an exception to the rule that "any player" should be interpreted as "any single player".

Cards

Fiery Torrent

Mages

Nemeses

Other

References

https://www.facebook.com/groups/AeonsEnd/permalink/2649853735233048/