Latin does have a bit of ergativity, e.g.
verto -are -avi -atum, i/to turn is a transitive verb, so it needs an object.
however, like in english, you dont always turn something, sometimes you just turn. the way latin expresses that is
Argus ad cenam se vertit, Argus turns towards the food, but more literally Argus turns himself towards the food.
because when you turn around, you are both doing the action, and experiencing the result of the action. which is what the sole argument of an intransitive verb does.
now, in latin, this is just to account for the languages accusative alignment, but maybe in a clong descendant of it (or in your own clong) that has more ambitransitive verbs,
Argus sē vertit becomes Argussē vertit becomes Argissē creating an ergative case
puer (nom) → puessē (erg)
puerī (nom) → puerīsse (erg)
penna (nom) → pennasē (erg)
pennae (nom) → pennaesē (erg)
flūmen (nom) → flumense
flūminēs (nom) → flūminēsse (erg)
hoc (nom) → hossē (erg)
haec (nom) → haessē (erg)











