New Horizons

Oracle Text

Enchant land

When New Horizons enters the battlefield, put a +1/+1 counter on target creature you control.

Enchanted land has "T: Add two mana of any one color."

Card Rulings

9/29/2017 You can cast New Horizons even if you control no creatures.
9/29/2017 If the land this Aura would enchant is an illegal target by the time New Horizons resolves, the entire spell doesn’t resolve. It won’t enter the battlefield, so its ability won’t trigger.