Step 1

Torn used Clear Gas! [Clear Smog + Corrosive Gas] (-33 EN)
All items were destroyed.
Crit? (1d24,24) - No (23)
Damage: 5+3+10-7=
11

Yveltal used Psychic!
Crit? (1d24,24) - No (23)
Effect (1d10,10) - Yes (10)
Damage: (9+9-7)*1.5=
17
Torn's Special Defense lowered! (-1, 3 turns)
Step 2

Torn used Thunderbolt! (-7 EN)
Crit? (1d24,24) - No (7)
Effect? (1d10,10) - No (9)
Damage: (9+3+10-7)*1.5=
23

Yveltal used Psychic!
Crit? (1d24,24) - No (7)
Effect (1d10,10) - No (4)
Damage: (9+9-7)*1.5+4=
21