Cross-class Subclassing
For D&D 5th Edition
Update: July 2022
An alternative to multiclassing, cross-class subclassing is the ability to take a subclass from another class than the one you chose at your character creation.
Every time you reach a level in your class where you can take a subclass feature, you may take one from an entirely different class. You don't get a choice of which feature you gain from that class though, you always start with the first feature(s) and work your way up if you chose that same subclass the next time you get the option.
Alternatively you could go for a different subclass from the same or from a totally other class, next time you reach a level in your class where you can take a subclass feature. But the same thing applies here, you start at the first feature(s) from that subclass.
The only class that works a little different here is the Cleric, both if you'd like a subclass feature from this class or if you play this class and if you want to speck in a subclass feature from another class the Cleric's 1st and 2nd level subclass features count as one.
Subclass Feature Exceptions
Sometimes when you take a feature from a subclass that is not your own, it expects you to already have a feature from your base class that you now do not have. Below is a list of those classes and features and how they work in this system.
Various Classes - Spells
If the subclass gives you a number of spells, you can cast those spells with the spellcasting ability from your base class. Be aware of the fact that, most of the time, you still do need spell slots to actually cast those spells.
The spells you get count as spells from your base class for you.
Subclasses like the Fighter's Eldritch Knight or the Rogue's Arcane Trickster also give you a set of spell slots, so you can use those even if your base class has none (like with the Barbarian or the Monk).
Barbarian - Rage
You can use the Rage-based features from the subclass without the Rage feature, but only twice per long rest, and it lasts for one minute.
The number of times you can use these features increases when you level: three times at 3th level, four times at 6th level, five times at 12th level, six times at 17th level, and an unlimited amount of times at 20th level.
Bard - Bardic Inspiration
You can use the Bardic Inspiration-based features from the subclass without the Bardic Inspiration feature, but only a number of times equal to your spellcasting modifier (minimum of 1) per long rest.
Cleric - Channel Divinity
You can use the Channel Divinity-based features from the subclass without the Channel Divinity feature, but only once per short or long rest.
The number of times you can use these features increases when you level: twice at 6th level, and three times at 18th level.
Druid - Wild Shape
You can use the Wild Shape-based features from the subclass without the Wild Shape feature, but only twice per short or long rest.
You can use these features an unlimited number of times at 20th level.
Fighter - Action Surge
You can use the Action Surge-based features from the subclass without the Action Surge feature, but only twice per short or long rest, and only once on the same turn.
Fighter - Second Wind
You can use the Second Wind-based features from the subclass without the Second Wind feature, but only once per short or long rest.
Monk - Ki
You get a number of Ki points to spend on Ki-based features from the subclass equal to your level.
Monk - Martial Arts
You can use the Martial Arts-based features from the subclass without the Martial Arts feature, your Martial Arts die is a d4.
The Martial Arts die changes as you level up: a d6 at 5th level, a d8 at 11th level, and a d10 at 17th level.
Paladin (Spellcasting, Channel Divinity)
You can use the Channel Divinity-based features from the subclass without the Channel Divinity feature, but only once per short or long rest.
Rogue - Cunning Action
You can use the Cunning Action-based features from the subclass without the Cunning Action feature.