MTX suggestion: Elder caustic arrow (and maybe Toxic Rain?)

Relatively simple idea:
A caustic arrow MTX that replaces the caustic ground with an effect similar to the visuals of the ground DOT effect the Squidges in the Uber Elder fight leave behind.

(It would be amazing if sb came up with an Elder version of Toxic Rain too so it's possible to combo these thematically. Maybe large eyes replacing the pods, with tentacles instead of vines latching onto enemies?)