Arcane focus influences both attack and damage? [closed]

Question

I'm working with the 5e basic rule set and have run into some questions about Arcane focus. I can't find where it is described, but from these forums I gather that wielding your focus allows for your proficiency bonus to be added to you spell attack roll. So d20 + ability mod + proficiency (when wielding arcane focus).

1. Does the proficiency damage also apply to spells? As in does Magic Missile do d4 + 1 + proficiency bonus? I know that it doesn't say it does, but I want to make sure I'm not missing something.

2. Does the arcane focus replace the need for components? Just got confused when you can choose an arcane focus or a component bag.

2a (bonus question) Does a component bag replace the need for components, or is it just a useful place to store them? If so, why not just store them in a pocket? What other bonuses does it grant?

Answer 1

First, question 0. Does wielding your focus allow for your proficiency bonus to be added to your spell attack roll?

No, you can always add your proficiency bonus to your spell attack rolls. The arcane focus allowing you to add proficiency was a rule back in the playtest which has now been removed in favour of allowing players to always add their proficiency.

Question 1. Does the proficiency damage also apply to spells?

No, it doesn't do this either. A spell does not gain your proficiency bonus to its damage unless it says it does. There are currently no spells that add your proficiency bonus to damage, although there are some that add your spellcasting ability modifier.

Question 2. Does the arcane focus replace the need for components?

Yes, it does, for components without a gold cost listed. This is the purpose of the arcane focus.

Question 2a. Does a component bag replace the need for components, or is it just a useful place to store them? If so, why not just store them in a pocket? What other bonuses does it grant?

The purpose of the component pouch is to handwave away spell components. Essentially, if you have a component pouch you don't need to care about the hundreds of bits of random crap you would have to carry to cast spells, although you still have to keep track of components with a listed gold cost. Without a component pouch or focus, you would have to keep an inventory of everything you needed to cast the spells you wanted to be able to cast.

Answer 2

No, proficiency bonus never applies to damage

The proficiency bonus is only applied to attack rolls, proficient saving throws, and proficient skills. Spells only deal the listed damage.

Yes, as long as no cost is listed or the component is consumed

According page 203 of the PHB...

A character can use a component pouch or a spellcasting focus (found in chapter 5) in place of the components specified for a spell.

It continues on to say that the focus cannot however be used if the components have a listed cost or are consumed by the spell and the component pouch cannot be used if there is a listed cost.

Yes, as long as no cost is listed

According to page 151 in the PHB...

...compartments to hold all material components and other special items you need to cast your spells, except for those components that have a specific cost (as indicated in the spell's description)

Thus the component pouch replaces all components except those that have a listed cost.