Slaughter Seasons

Overview
"Slaughter Season is atype of Ice Season in which you need to earn Pennants by Icing opponents to build your reputation and score Reputation Badges.

The Reputation Badges in Slaughter Season are similar to the Ice Seasons. Ice opponents on Fight List to earn Pennants and build your reputation each week. There are five mastery tiers (Bronze, Silver, Gold, Ruby, and Diamond) and each have five levels and thus a total of 25 badges. At the end of each season, your badge ranking will be determined by the number of Pennants you earned for that week.

Pennants can be earned through icing opponents in any City and are required to earn Reputation Badges. This is different from the normal Ice Season where Ices are directly counted for the progress and earning of Reputation Badges. The Number of Pennants you can earn by Icing an opponent depends on their difficulty level.
 * Earn 1 Pennant per Ice by Icing an Easy opponent
 * Earn 2 Pennants per Ice by Icing a Medium opponent
 * Earn 3 Pennants per Ice by Icing a Hard opponent
 * Earn 1 Pennant per Ice by Icing a Miniboss

Ices earned through the Arena do not count."

- Mafia Wars Blog

Seasons
Overview of Mastery Rewards for each of the slaughter seasons, attack and defense values represent maximum values for a fully completed ice season. Each slaughter season runs for 1 week awarding the mastery reward at the end of the week. For more details on each slaughter season and it's milestone (progress) rewards check the individual pages.

Badges
Depending what level of the tier you get to will determine what badge you will receive. You will be notified at the end of each season when collecting your mastery item which level & tier badge you will receive. Your badge will show on your user profile like this:

Your badge will also appear next to you name on the fight list. You will see other users who have obtained a badge on your fight list like this: