The final component of a spread is the teaser. An optional extra some anglers swear by them, while others (myself included) see them as just another thing to pull in when you get a strike. Love them or hate them teasers certainly do play a role in offshore trolling.
The primary role of a teaser is to draw the fish into the spread. Once the fish is raised the fish should divert their interest away from the teaser and onto the lures.
Just about anything can be used as a teaser including deep diving mirrors, such as Braids Lighting Bolt, through to a surface skipping daisy chain of pink squids.
As a basic rule anglers fishing offshore chasing bigger marlin like to run diving teasers which vibrate and flash. While anglers fishing inshore, chasing small marlin and sailfish, prefer surface teasers. Having said that there are no set rules in fishing and experimenting will help to make you a better fisherman.