UP_TRIGGERS provides spell-writers the opportunity to use sorcery's
up_trigger function, which allows runtime registration of
up_trigger function has two parameters: the 'target' spell to run the trigger on, and what trigger 'action' to run. When a spell calls
up_trigger, sorcery registers the request where it will later be used by the build phase of cast. After the spell is built, cast will subsequently execute the trigger action. If multiple target/action pairs exist, no build order is specifically enforced by sorcery.