Ruby of the War Mage 5e & Spellcasting Focus

Ruby of the war mage 5e in dnd is a Wondrous item, common (requires attunement by a spellcaster.) A spellcasting focus is an object or symbol that spellcasters use in Dungeons and Dragons 5e for certain types of spells.

Ruby of the War Mage 5e

Carved with eldritch runes, this 1-inch-diameter Ruby enables you to use a martial or simple weapon as a spellcasting focus for your spells. For this feature to work, you must connect the Ruby to the weapon by pushing the Ruby against it for at least 10 minutes. After that, no one can remove the Ruby unless you detach it as an action or the weapon is destroyed. Not even an Antimagic Field causes it to fall off. The Ruby does fall off the weapon if your attunement to the Ruby ends. Source: Xanathar’s Guide to Everything.

What is the cost of Ruby of War Mage 5e?

I’d price it somewhere between 50 and 100 gold and not allow it as a starting equipment. It is a common magical item. I wouldn’t let a level 1 character start with a magic item, as it just doesn’t feel fair to the likes of your barbarian, your monk etc.

It’s a common magic item, so in the DMG, it costs about 100gp. I wouldn’t price it like a potion because it is not consumable. You may ask the DM if you can find one in the next treasure horde. Or maybe everyone can start with a standard magic item from XGtE?

An acceptable cost of Ruby of War mage and common items

Can an Eldritch Knight use a Ruby of the War Mage?

How does an arcane focus in dnd work with an Eldritch Knight? Eldritch Knights may not use an arcane focus as a spellcasting focus.

Ruby of the War Mage 5e (XGtE p. 138), however, states:

Etched with eldritch runes, this 1-inch-diameter Ruby allows you to use a simple or martial weapon as a spellcasting focus for your spells. 

This paragraph doesn’t mention anything about arcane foci. But it straights up says that you can use the weapon as a spellcasting focus. The only requirement is that you are a spellcaster (which is valid for Eldritch Knights).

Yes, the Eldritch Knight can use a 5e Ruby-red Weapon as a focus.

You don’t need a unique feature to use a spellcasting focus. You usually need a feature that lets you use X item type (arcane or druidic focus, musical instrument, tools, sword, etc.) as a spellcasting focus. The Ruby comes with its feature letting you use it.

The general rule which covers the use of spellcasting focuses is in the Component Rules of spellcasting.

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

— Player’s Handbook; Chapter 10: Spellcasting; Casting a Spell; Components; Material (M)

However, by default, there isn’t anything that is always a spellcasting focus. That gets defined by a feature (or sub feature of the Spellcasting feature) for the specific caster.

Spellcasting focus 5e

The Ruby would be one such feature (creating an additional, specific rule for the relevant character) that lets you use the particular weapon as a spellcasting focus. Perhaps of note, it is not the only feature that allows a weapon to be used as a spellcasting focus. See the College of Swords and their Bonus Proficiencies feature (also from XGtE).

A spellcasting focus is an object or symbol that spellcasters use in Dungeons and Dragons 5e for certain types of spells.

A spellcaster has three options to cast a spell using a material (M) component.

They can use the following: (1) the spell components, (2) the component pouch or (3) a spellcasting focal.

It is best to use the pouch or focus for spellcasting.

The component pouch, also known as a spellcasting focus, is intended to simplify the game. It removes any spell components with a specific cost, usually in silver or gold pieces.

Depending on the class of the caster, a focus can take many forms.

Classes and Focus Rules

Arcane casters are wizards, sorcerers and warlocks who use a crystal, rod, staff, orb as their arcane focus. A druidic focal point is something like a sprig, mistletoe or totem, staff, or yew-wand. Clerics, paladins, and others can use holy symbols as spellcasting centres, such as an emblem, reliquary, or amulet.

These focuses have prices that can be visible in Chapter 5 of the Player’s Handbook.

Certain classes and subclasses have specific rules regarding the use of a spellcasting focal point.

Bards, for example, can focus on a musical instrument, while College of Swords bars can focus on their weapon. Artificers can use a toolset as a focal point.

When using a component pouch or spellcasting focus, the most important thing to keep in mind is using it. You will need a free hand. You can use a two-handed weapon, but you must remove one hand to access your focus or component pouch.

Clerics and Paladins have the option to wear their holy symbol or keep it on their shield. They don’t need a free hand to cast spells using a material component unless that component has an associated price.

Remember that spells with somatic elements (S) require a free hand. That can be the hand used to access the spellcasting focus or component pouch.

Characters who use their weapon or shield to focus can cast spells with both (M and (S), but they must have another hand free to cast a spell that has only (S), such as cure wounds.