Potion of Invigoration
From RoR Wiki
The Potion of Invigoration is an item that doubles the drop rate in RvR for 30 minutes when used.
This item is granted exclusively for winning the RvR Random Event "Ravenous Rage".
In particular, this item is helpful for gaining more War Crests upon killing enemy players, as high Renown Rank players have set chances to drop war crests, but rarely drop the maximum. With this item active, the odds go up considerably.