Paul moves up behind Polina, throwing a wooden ball into the room as he fires with his shoulder weapon, and backing up as it hits and the compression field keeping the air inside bottled up explodes.
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Eldritch Cannon (1d20+8)[9] or (1d20+8)[25] for (2d8)[7] force and a 5' pushback at the closest enemy.

Shatter (3d8)[11] thunder damage + (1d8)[7] from arcane firearm (not sure if applies to all damage or just 1; only making 1 damage roll, so all?), Con DC 15 half
Hitting the bottom 4, or if the closest enemy gets killed by the cannon, the top 4.
Con saves
(1d20)[2]+??
(1d20)[9]+??
(1d20)[12]+??
(1d20)[13]+??