One of the best things about Ranger-Captain of Eos is that it has a powerful ability that can help us protect our creatures, or prevent our opponents from countering our spells
While it pairs exceptionally well with your commander to give it protection and untap your lands, its power comes from the fact that you can get infinite combat phases if you can reliably hit with the equipped creature
The Celestial Tower Plane: Zaegoth At the beginning of your upkeep, you gain X life, where X is the number of cards in your hand minus 1
This means that you have access to all of green's land ramp, white's catch-up and taxes, red and black's rituals, and tons of mana artifacts
While there are seven of these cards in total (including Captain Kirk and Captain Janeway so far), only 200 or so have been made for each one across the entire MTG Star Trek range