Victory in Hillsbrad

This Achievement now awards the title [title=418], and the Alliance version, found here: Victory in Hillsbrad, awards a title, [title=417].

From the Official Blog

A win will gain you a shiny new title: either Tarren Mill Terror for the Alliance or Southshore Slayer for the Horde.

The blog seems to indicate that Southshore Slayer will be the Horde Title, and Tarren Mill Terror the Alliance Title.

This Achievement is now a Feat of Strength, considering the short time it will be available.

[npc=76873], the savage battle pet who used to be the reward for this Achievement, was just a placeholder, and is not currently obtainable by any means.

The title, [title=418], is account-wide, including both factions.

Earning this Horde-side achievement also gives your Alliance characters access to the [title=417] title.

Appears to require the character be level 90 to use the title.

If you can't find SS vs TM in your battleground list, try again in your garrison. It's the only place where it actually appears for me. Not sure if anyone else got the same problem.