Secrets of Toanium

Some items will add a second attack that takes place after their owning character makes an attack.

This needs to be implemented. It could be done as a "secondary attack", and/or we could add an "afterAttack" trigger, that also calls back out of the isolate and could be used for a variety of things, including a secondary attack.

I prefer the former, but we need to evaluate carefully whether we need an "afterAttack".