Defender, reach Whenever you attack, create a 2/1 colorless Construct artifact creature token with flying named Ballistic Boulder that's tapped and attacking. Sacrifice that token at the beginning of the next end step.
The trebuchets would be destructive enough even without the fire.
![Fire Navy Trebuchet [Avatar: The Last Airbender]](http://www.cardmerchanttakapuna.co.nz/cdn/shop/files/6c8488c8-6fe2-520c-9897-603bf02bb420.png?v=1777063794&width=1445)