Can you take different archetype options at different levels?

Question

Once you've picked a subclass option at level 3, could you later take a different subclass option, or do you lock into a specialty at level 3 and then run with it for the rest of that class' progression?

For example, as a rogue, if you took the "Thief" archetype at level 3, giving you access to Fast Hands and Second Story Work, could you then take the "Assassin" archetype to give you the specific benefits that archetype gives instead of the "Thief" ones?

The PHB rogue description seems to imply that you couldn't:

At 3rd level, you choose an archetype that you emulate in the exercise of your rogue abilities: Thief, detailed at the end of the class description, or one from another source. Your archetype choice grants you features at 3rd level and then again at 9th, 13th, and 17th level.

but I'd like a more certain answer, especially one that refers to archetypes in general. Also I'm not ashamed to admit I'd prefer a source with some authority that tells me you can mix and match, but I am looking for the truth of the rules when all is said and done...

• Different to Can you multiclass the same class twice for different class features because the no on that demonstrates that you can't re-take a level of the same class. Taking different features for different levels is not the same thing, and would work differently.

• Similar to Can I mix monk traditions? but that one was specific to monks - which is why it didn't show up on any searches I did, and why it wouldn't on the searches of others. This question is specific enough to be clear and precise, but broad enough to be useful to others who aren't in the exact same situation/using the same class.

Answer 1

Short answer, you're locked in.

You can only choose one archetype per class, and there are no current rules that allow you to pick-and-choose features from different archetypes.

If you want to diversify your character's build, you can look into multiclassing. This lets your character pick up levels and features from different classes.

Note: You cannot multiclass into the same class to get additional archetypes (relevant Sage Advice).

I would recommend taking a read of this article: Modifying Classes. Whilst it doesn't discuss exactly what you're after, it might help. Specifically, the part on Creating New Class Options.

One way to get what I think you're after is to create a new Roguish archetype. It's a bit of a cop out, but with your DMs blessing it would definitely work. You'd have to come up with a very strong reason why your class would be meshing two existing archetypes (Thief & Assassin) though; and from a balance perspective you could come across certain situations where your character has too many tools at its disposal compared to other PCs which stuck to a single class option. Once again, discuss with your DM.

Back to the article, the key takeaway is this:

Take a look at the class’s existing options and see what they provide, and then use those as examples or building blocks for the features that your class option will provide. It’s perfectly fine for two class options in the same class to share some mechanics, and it’s also appropriate to examine other classes for mechanics you can draw upon for inspiration.

If you get an okay from the DM to create your Thiefsassin, you could utilise the Thief features for 3rd and 9th level, and the Assassin features at 13th and 19th level.

Answer 2

No; you can only pick one subclass.

You get the Roguish Archetype class feature at rogue level 3, which lets you pick one subclass. You never get the Roguish Archetype class feature again, and can't change your choice later. That archetype gives you some immediate (sub)class features at 3rd level when you pick the subclass, and gives you additional features at 9th, 13th, and 17th level. However, you never get the feature again, and the feature never lets you change your choice later.

The same applies to other classes, with the subclass choice potentially occurring at a different level.

(The only exception to this is if your DM lets you retcon your past choices. Some might allow you to do so once at an early level, but this is not a given. Other times, your character may experience events in the story that prompt a change in their paladin's oath, their warlock's patron, or their cleric's deity - and your DM may allow your character to change their subclass to reflect that. However, do not expect such changes to be automatically allowed; choose carefully.)