There have been quite a few 25/27 Commander lists coming out in the recent past, and I've always been tempted to set one up myself. Sadly, I never really had an idea for a good topic – until recently Korakhos came up with an awesomely inspiring CotW challenge.
As of Ixalan, there are 238 official creature types (Un-types not counted) in Magic, with only 101 of them appearing on legends. This collection of 27 commanders looks at all those creature types not yet featured, and gives them a chance to shine! Also the cards feature some official mechanics, personal additions as well as a few ones from the MSE community.