Thor's Hammer
From WikiRaider
File:Example.jpg
A Naga, as seen in the official Promotional image from eidos
Thailand's loading screen suggests that the only way to enter helheim is by using the Mjolnir,Lara also says in the gameplay trailer that she needs it to kill a god(Fans speculate that this god would be Natla but this is unconfirmed).
Even if Natla isn't the god Lara was refering to,now she has the means to finish her off once and for all(what she couldn't do on the first game). She may also be relating possibly to the god of the Underworld, Hel,the daughter of Loki. According to recent updates(whether official or not)Lara will find the hammer in valhalla,and by then,she will already bear the gloves and the belt.