2022-09-09 : As Stronghold Arena’s last ability resolves, you don’t get to see what the card of your library is before deciding whether to reveal it. If you choose to reveal it, you must put it into your hand and will lose life.

2022-09-09 : Normally, combat damage is dealt all at the same time. In that case, Stronghold Arena’s last ability triggers once for each opponent that creatures you control dealt combat damage to, regardless of how many creatures were dealing that damage. If any of those creatures have double strike or first strike, the ability will trigger once for each opponent dealt damage in each combat damage step.

2022-09-09 : You may kick Stronghold Arena only once for its {G} cost and only once for its {W} cost. You can kick it twice by paying {G}{W}, but you can’t kick it twice by paying {G}{G} or {W}{W}. You can’t kick it more than twice.