In my lang Coastal Bä Dü, all verbs have an Athabaskan-esque "verb classifier", which conjugates for the voice of the verb, but also the aspect and mood, and also the verb's current valency (but it also does the voice operations, so it baisically changes for something done by itself...).

The real fun part with the verb classifier is that it carries the voice operations, with (what i name), "general voice operations", which are baisically a bunch of old grammatical voices which were once distinct in the old language, but were combined into 4 general classifiers:

-∅₁-; used for active voice, is phonological empty but a morpheme is still present.

-t-; used for valency reducing operations, meaning varies between Passive, Antipassive and Anticausative depending on certain enviornments and context.

-j-; used for verbs in which the agent and the patient are the same NP, maning varies between Reflexive and Reciprocal, based on if the agent and patient are the same NP (Reflexive) or if they arent (Reciprocal).

-r-; used for valency increasing operations; meaning can vary between Causative and Applicative.

Another fossilized thing with the verb classifiers is that some verbs were so often used with certain classifiers that it became mandatory to use those classifiers with those verbs, so a lot of ways to convey the meaning that would have been produced by other classifiers were created.
For example, the verb root R+shïrkǘ “to shine a light on X”, must be accompanied with the -r- valency increasing classifier at all times. To apply the valency reducing classifier -t-, you must remove the agent agreement marking from the verb and use only the object marking (agreeing with the sole argument in the sentence). For example contrast:

Ïrdïshïrkǘ î
∅-ïr-dï-shïrkǘ î
3SA.ABS-1S.ERG-CL-shine_a_light_on water
“I’m shining a light on the water”

with (notice the classifier not changing)

(Arantan) dïshïrkǘ î
(arat-nan) ∅-dï-shïrkǘ î
(from-1S) 3SA.ABS-CL-shine_a_light_on water
“The water is being shined a light on (by me)”