The Slot Machine
Casters who have positive modifiers on their key casting ability have additional spell slots available at each level per the table Bonus Spell Slots.
For a multiclass spellcaster, use the highest key ability to determine extra spell slots per the Spell Slots per Spell Level chart in Chapter 6 of the Player’s Handbook (p.165 in the 2018 edition).
Bonus Spell Slots
| Key Mod | Bonus Spell Slots | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | |
| +1 | 1 | — | — | — | — | — | — | — | — |
| +2 | 1 | 1 | — | — | — | — | — | — | — |
| +3 | 2 | 1 | 1 | — | — | — | — | — | — |
| +4 | 2 | 2 | 1 | 1 | — | — | — | — | — |
| +5 | 2 | 2 | 2 | 1 | 1 | — | — | — | — |
| +6 | 3 | 2 | 2 | 2 | 1 | 1 | — | — | — |
| +7 | 3 | 3 | 2 | 2 | 2 | 1 | 1 | — | — |
| +8 | 3 | 3 | 3 | 2 | 2 | 2 | 1 | 1 | — |
| +9 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 1 | 1 |
| +10 | 4 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 1 |
The bonus spell slots don’t work precisely the same for warlocks since they only ever have one level of spell slots available. Instead, a warlock gets a number of bonus spell slots from their current level plus their ability modifier, e.g. a 1st level warlock with a +2 key ability modifier (see Warlock Versatility) can cast three additional 1st level spells, while the same caster at 5th level could cast four additional 3rd level spells.
Added to House Rules in 2023.