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Mummy would be a good secondary ability for CAP 20 for several reasons. Firstly, it heavily favours CM over DD which I believe is important due to that I, like several others, think that DD at the moment kind of overshadows CM and thus the secondary ability favouring CM would assist the concept...
A couple of abilities that I'd like to bring up that are inferior to water veil but are still potentially useful that have not yet been mentioned are Mummy, Shield Dust, and Compound Eyes. Mummy helps discourage physical pokemon that rely on their abilities, such as technician users (Scizor...