Where to find the secret weapon mentionned in the devblog.
How to Find Secret Weapon
First off you need to travel to the Charcoal Spill biome added in the latest patch (at this time), and reach the old charcoal bag.
You will need gear in order to resist the burning heat (Antilion armor and/or the Mutation you get from eating ice candies).
Get in the Bag
Find a hole to get inside the bag, probably slightly underneat from a trench in the dirt.
And then, slightly to the left you will encounter a little cluster of charcoal. The weapon is stabbed in the burning one.
There It Is, Boys!
It’s been a few days and I don’t quite remember clearly what happens next, if you get a broken version or the blueprint, but this is the weapon. A blazing hot two handed asian sword. Spicy damages, and provide a little bit of light at night.
And for your convenience, here is the blueprint.