Furnace within is a spell from Races of Eberron that comes with a certain 'mindset'. This means that as long as a wizard (or other prepared caster that can cast this spell) has this spell prepared, they benefit from a certain bonus. In the case of Furnace Within, this bonus is as follows:

Mindset: The energies you manipulate while preparing this spell cause an intense heat to well up within you. Although it doesn't harm you, this heat makes your unarmed strikes, natural weapon attacks, and melee attacks with metallic weapons deal 1 point of fire damage in addition to their normal damage. This heat dissipates when the spell is cast.

If a Wizard has this spell prepared multiple times, would this bonus stack? And would this bonus stack with other things that grant extra fire damage to a weapon, such as a crystal of energy assault?

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    \$\begingroup\$ Cheers for showing me something new; I had never heard of these mindset spells before. I added the source in, because Google was having a hard time finding it for me (“furnace” and particularly “within” being rather common words, after all!). \$\endgroup\$ – KRyan Feb 6 '18 at 15:22

No, it would not self-stack. Though the bonuses are untyped, they all come from the same source (the mindset of furnace within), and so do not stack. Basically, effects can only self-stack if they explicitly say they do.

Relevant rule, from SRD > Basics > Stacking:


In most cases, modifiers to a given check or roll stack (combine for a cumulative effect) if they come from different sources and have different types (or no type at all), but do not stack if they have the same type or come from the same source (such as the same spell cast twice in succession). If the modifiers to a particular roll do not stack, only the best bonus and worst penalty applies. Dodge bonuses and circumstance bonuses however, do stack with one another unless otherwise specified.

(emphasis mine)

Neither the rules for furnace within nor the rules for mindset spells (Races of Eberron page 180) suggest any exception to this general rule for this case.


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