Spellcasting Monsters in Level Up
One of our goals with the Level Up: Advanced 5th Edition Monstrous Menagerie was to make enemy spellcasters less of a pain to run. With an updated stat block format, we've made it possible to run a complex battle without looking up spells in another book or online resource–all while working as expected with existing spells and features like counterspell and antimagic field.
As an example, here's our NPC priest stat block:
In Level Up, if a monster or NPC's spell is likely to see use in combat, we include it as an action (or reaction, or bonus action) in their stat block. For instance, in the priest's stat block, spirit guardians is fully detailed as an action, just like their mace attack. You don't need another book or an online tool to run a monster.
Spells are spells
The spirit guardians action is listed in the priest’s Spellcasting trait, which means that it's a spell. It interacts with the usual spellcasting rules: a rival priest can cast dispel magic on it, and the priest can't cast it and healing word in the same turn. It doesn't break or ignore any of the usual rules of the game.
Our stat block also notes that spirit guardians is a concentration spell (so whack that evil priest and force a concentration check!), and we list its spell components of V, S, and M (someone cast a silence spell!)
Guidance for the Narrator
We don't convert every spell into an action. That would lead to unmanageable, multi-page stat blocks. If it's a utility spell or it's not usually worth casting in combat, then it appears only in the monster's spell list and not as an action. You might find a clever use for a utility spell - or want to look up additional rules, like how to cast a spell with a higher slot. In that case, you'll have to consult the spell description. Most of the time, though, you can run a monster quite efficiently without consulting another book.
Powerful spellcasters have a lot of options! That's a feature of the game, not a bug. Our most complex spellcaster, the lich, has 22 spells prepared, of which nine are detailed in its stat block. Still, the lich stat block fits handily on one page spread - with room left for a section of combat advice.
Between our various stat block changes–the curated list of spells in the stat block, the notes for concentration and components, and the combat advice–Level Up lets you run every spellcaster, even a complex and high-level one like a lich, with zero prep.
We're proud of our spellcaster format. Rather than inventing new tech that changes the way the game works, we've polished the presentation to provide maximum usability. We think it's going to be the state of the art for quite some time.