Recommended For: Political decks like Kenrith, the Returned King, Xantcha, Sleeper Agent, and Queen Marchesa
Since typical Limited decks need their first 3 land drops, would like to hit their 4th land drop, but dont necessarily need 5 lands by turn 5, the age-old standard of 17 lands indeed seems like a good number
This is true even if you use the mana to pay an additional cost while casting a spell "without paying its mana cost." (2018-12-07) You must choose an existing creature type, such as Human or Warrior
Obviously, this isnt worth much if your creature is small, but on something like Okaun, Eye of Chaos or Primeval Spawn, youre going to be cooking with a large payoff and little downside