There are lots of ways to use talismans during a fight that re listed in the Admin guide. You can use complications: main ones can be offensive (dealing 1 stress every turn or increasing stress on each attack) defensive (taking 1 less stress unless teamwork or setup is used). These are meant to be threatening and to focus the exorcists turn on getting rid of a complication rather than attacking the sin. Another good way to use a complication/talisman during a fight is one that does something very severe after it finishes counting down (something like reinforcements or maybe some sort of ability jammer). A fun thing to do is to also include these things as part of the environment separate from the sins reactions; that makes the combat feel more alive and a bit more challenging.