Id definitely recommend EDHREC as a great resource for more card recommendations for when you go to build your Treasure deck.
Team Avatar Enchantment Whenever a creature you control attacks alone, it gets +X/+X until end of turn, where X is the number of creatures you control
The reason is explained in this article, but the general reason is that lands are best for casting your commander and ramping, outside of that they have very little function
Its base power and toughness are 4/4
While only getting the full use of your lands every other turn is a huge downside for this effect, cards like Seedborn Muse or Wilderness Reclamation trivialize it, ensuring you can put out huge creatures that your opponents will struggle to deal with while avoiding the risk of leaving yourself open to do so
Impact and water-resistant design protects against accidental spills and drops