When a void spell echoes due to the VK mastery bonus (including echoing strikes, time legion, and avatar of regret) it always procs a devouring orb. My expectation was that the spell you cast would be echoed.
I first noticed this with abyssal echoes causing devouring orbs to be created. Turns out it also works when toggling ravaging or ephemeral stance since they are ‘void’ and ‘spells’. Here’s an example:
Further data point, this behavior is only true for Abyssal Echoes if you have the node that makes it instant cast. If it is NOT instant the echo will be a cast of Abyssal Echoes. If it IS instant, the cast will be your last non-instant attack or void spell.