Casting a Spell: The Parts Nobody Talks About
Spellcasting has more moving pieces than most players bother to track, and the ones that get ignored are usually the ones that matter most in a tight spot.
Casting Time
Most spells take an action, which is straightforward. Bonus action spells are where it gets interesting, and slightly frustrating: the rules say if you cast a spell as a bonus action, the only other spell you can cast that turn is a cantrip with a 1-action casting time. One spell slot, one non-cantrip spell per turn. That’s the rule as written, even if your players occasionally discover two spells that would be spectacular together and stare at you like you’ve personally wronged them.
Reaction spells, like Counterspell, are rare enough that when one comes up it always feels like a treat. They exist because some spells genuinely wouldn’t work any other way.
Then there are the long ones: 1 minute, 10 minutes, 1 hour. These are not combat spells. If you find yourself casting something with a 10-minute casting time in the middle of a fight, you are spending 100 turns concentrating while your party presumably dies around you. Legend Lore has a 10-minute casting time, which is the example spell for this episode, and nobody is casting Legend Lore in a dungeon encounter unless they have extremely patient friends.
Components
This is the section most tables quietly skip, which is a shame because it’s one of the best tools a DM has.
Verbal components mean you have to be able to speak. A Silence spell, or honestly just a bag over the head, shuts down every spell with a V component. Somatic components mean at least one hand has to be free. Tie a caster’s hands, and you’ve neutralized most of their options. Strip their component pouch, and you’ve taken care of the rest. Spellcasters are powerful, but they are also fragile in ways the rules spell out clearly if anyone bothers to read them.
Material components come in two varieties: those with a listed gold value, and those without. The ones without a value can be covered by an Arcane Focus or Component Pouch, which most spellcasting classes start with. The ones with a gold value have to be found or purchased explicitly. Some are consumed on casting; some are not. For Legend Lore specifically, you need incense worth at least 250 GP per cast (consumed) and four ivory strips worth at least 50 GP each (not consumed, so once you have them, you have them). A clean way to handle consumable components without drowning in inventory management: just track them as uses. You don’t need to roleplay buying incense sticks. You have three casts of Legend Lore. Mark it down and move on.
Duration and Concentration
Instantaneous spells do their thing and they’re done. They also cannot be dispelled, because there’s nothing left to dispel. Dispel Magic needs something with an ongoing duration to have any effect.
Spells with a duration are not automatically concentration spells. Blindness/Deafness lasts a minute with no concentration required. Zone of Truth runs for 10 minutes without it. The concentration tag will be listed explicitly in the spell if it applies.
When a spell does require concentration, two rules matter most. First, you can only maintain one concentration spell at a time. Fly and Invisibility are both concentration; you cannot have both running at once. Second, every time you take damage while concentrating, you make a Constitution saving throw against a DC of 10 or half the damage taken, whichever is higher. At high levels, against serious damage, that DC climbs fast. A dragon breathing fire on a concentrating wizard is not just dangerous in the obvious way; it’s potentially unraveling whatever spell they were holding together.
For the Player’s Handbook reference on all of this, Chapter 10 covers the full rules for casting spells.