- Pay attention to material costs of spells, this helps keep spellcasting in line with other characters/classes -- more importantly, it helps prevent (or at least slow) abuse cases.
- Similar to the first part, spells have material and somatic requirements. Focuses can satisfy both of these requirements in most situations but make sure the caster is using the correct focus. This is a minor check on multiclassing strategies (specifically between the Artificer and Wizard as they use different focuses to cast their spells).
- Why should you be adament about this? Artificer has access to a ton of spells across multiple classes the wizard does not -- Guidance, Faerie Fire, Cure Wounds. This allows the Wizard to outclass clerics, druids, and rangers in just about every way.
- It's annoying and maybe it's a little petty but it at least forces the multiclassed character to make decisions as to what spells they want to use (or sacrifice 2 AC and an action to remove the shield)
- There are feats and class features that help make spellcasting fluid for the casters that are designed to be gish/tanky (clerics and paladins can already use their shield... The War Caster feat further allows weapons to be used as a spell focus... The Hexblade has an Eldritch Invocation to make their weapon a focus)... All of these have costs to them, don't give it away for free. You're almost always going to make a different class weaker while making another class more powerful.
A general rule of thumb is in order to cast a spell, you need a free hand or be holding a focus appropriate for your spellcasting feature to cast a spell.
TODO: List out the appropriate focses for each class.
How to get around this: Artificer Initiate, War Caster... Dropping your current focus (not swapping them)
Remember, I'm a big fan of multiclassing but I also believe multiclassing requires trade-offs (and not just learning spells a level later). There are a lot of dips that function as at least one feat (if not more), which is something that should cost 4 levels instead.
Wands and Staves should be Arcane Focuses but it is not RAW. RAI, certain items say they can be used as a focus but no staves or wands have this text (this heavily impliess wands and staves are arcane focuses)
Casting Spells with Scrolls (when you can't cast it yet)
https://www.youtube.com/watch?v=nk1Up4hXUko
Racial Bonuses and Spell Casting Components
https://www.dndbeyond.com/forums/dungeons-dragons-discussion/rules-game-mechanics/24911-racial-spells-material-components https://www.sageadvice.eu/is-it-intended-that-you-should-have-the-material-components-for-spell-you-know-from-your-race/amp/