Board Thread:General Discussion/@comment-31283382-20140611172614/@comment-5553481-20140731101021

He doesn't need to use the mask anymore, because 'Quincy' Zangetsu isn't limiting his power, meaning Ichigo's at full power from the start (not counting bankai)... The mask most likely worked like a 'limit release'...

The mask wouldn't suprise Yhwach either way, because the Vandenreich were researching the 'war potentials' for years.