Merrow

The mythological merrow are Irish versions of the common merfolk. Their only noteworthy features are that the males are hideous, provoking females to woo human sailors instead, and always wear a magic hood that works similarly to a selkie's skin. If you steal their hood, they cannot return to the waves and you can extort them to marry you or something. Since the tales are limited to men stealing the hoods of merrow maids, it is unclear if merrow men have hoods as well.

3e merrow are simply aquatic ogres. This portrayal was carried into Pathfinder, which introduced freshwater and saltwater variations.

5e merrow are evil counterparts of standard merfolk, similar to the merrow (aka murdhuacha) in Changeling: The Dreaming. Or the deep merfolk in Pathfinder.

Speaking of which, Changeling: The Dreaming distinguishes between merfolk and merrow on the basis that the former are part vertebrate and the latter part invertebrate. I burrowed this idea in order to condense the merfolk races, as I mentioned in an earlier post.

Anyway, I think there is room for both versions of merrow and more. They might need renaming, such as to "aquatic ogre" and "dark merfolk" or something along those lines.

Links

• https://1d4chan.org/wiki/Merrow
• http://whitewolf.wikia.com/wiki/Murdhuacha
• http://dailybestiary.blogspot.com/2012/12/merrow.html