Spells and Items during combat

Question

It is quite clear that an investigator can only use one item that gives the highest bonus in combat, even if they have multiple items (i.e. Multiple weapons)

However, what about spells such as Wither? We must first test Lore to see if we get a bonus and then flip the card and fulfil additional effects based on our results. Its possible that you don't get the bonus due to failing the test.

Does this count as the component that you used for combat and you cannot use any other items, even if you failed? Or is it special since the spell doesn't give a plain combat bonus like regular items?

Answer 1

From the reference guide, page 11:

He may use one effect that provides a bonus (for example “Gain +3 Will”). If multiple effects provide a bonus, he uses only the highest bonus.

This wording implies that when multiple effects are available he uses the highest bonus, not that he strictly uses the effect with the highest bonus potential. It implies to me that all the effects are in play and overlapping. Narratively it supports the idea that multiple items operate concurrently, an idea also supported by the fact that items that grant rerolls can accumulate. This is how we have been playing.

Note that choosing to use Wither comes with its own cost when it fails, so there is already a penalty when it is attempted and failed.

Answer 2

This becomes clear when you're aware that gaining a bonus isn't the same as applying a bonus.

Wither may have you gain a +3 bonus if you succeeded on the Lore test.
At the same time Hired Muscle may have you gain a +1 bonus, no strings attached.
All in all, you may gain any number of bonuses to a given test.
Then, you apply exactly one of these bonuses – the highest one.

If you failed to cast Wither, this just makes you not gain this particular bonus.
If you have gained some other bonuses, you'll apply one of those.