Elephant Grass
Enchantment
Cumulative upkeep 
(At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Black creatures can't attack you.
Nonblack creatures can't attack you unless their controller pays 
for each creature they control that's attacking you.
"How have I angered nature that she would imprison me in a labyrinth of grass?" —Kasib ibn Naji, Letters
Tony Roberts
Visions (VIS)
• #104Rulings
Unless some effect explicitly says otherwise, a creature that can’t attack you can still attack a planeswalker you control.
(wotc • 2014-02-01)
Rulings
Unless some effect explicitly says otherwise, a creature that can’t attack you can still attack a planeswalker you control.
(wotc • 2014-02-01)