The helm for Siris is a turkey head that also includes a top hat and a monocle, while the hat for Isa is a turkey head with a bow. The helms, which are provided to players for free, will boost experience and skill points earned while they are worn.
The Turkey Helm will be available in Infinity Blade III for a week, after which time it will be unavailable. Infinity Blade III can be downloaded from the App Store for $6.99. [Direct Link]
The original Infinity Blade game is also available for free this week as part of a Black Friday promotion. [Direct Link]