Whenever Bane of Bala Ged attacks, defending player exiles two permanents he or she controls.
The continent of Bala Ged was ravaged by massive Eldrazi of Ulamog's lineage, its lush jungles and cascading rivers reduced to dust.
If Bane of Bala Ged attacks a planeswalker, the defending player may exile that planeswalker. Bane of Bala Ged will still be attacking and may be blocked as normal. If it's not blocked, it won't deal combat damage.
In a Two-Headed Giant game, you choose which of your opponents will exile permanents. You can't have each of them exile one permanent.
The permanents are exiled before blockers are chosen.
If the defending player controls only one permanent, that permanent will be exiled.