Other tapped creatures you control get +1/+0. Other untapped creatures you control get +0/+1. Whenever you attack, untap each creature you control, then tap any number of creatures you control.
2021-04-16
Augusta's last ability triggers whenever you attack with any creatures, even if you didn't attack with Augusta.
2021-04-16
Augusta's last ability untaps all creatures you control, not just the ones that attacked this turn. Then you choose which creatures to tap, if any.
2021-04-16
Despite the term "other tapped creatures," Augusta's first ability doesn't care whether Augusta is tapped or untapped. The same is true for the second ability. Both abilities apply as long as Augusta is on the battlefield.
2021-04-16
Plargg, Dean of Chaos's second ability allows you to cast the spell during that ability's resolution, ignoring its normal timing restrictions.
2021-04-16
Untapping an attacking creature doesn't remove it from combat. It's still attacking normally.