A Traveller's Seal will open certain locked doors in Cronos, and you'll find your first in the underground station during the 'find a way to open the gate' objective. You'll have probably seen a couple of doors sealed with red locks that looks like they need a Cronos door code by now, but instead of seeing a keypad when you interact with them they will open your inventory. So what's going on?
How to open locked doors in Cronos with a Traveller's Seal
The first sealed door you'll find in Cronos, with a red lock on it, is in the underground station section alongside a door behind some biomass goop blocking it, and a door boarded up with planks.
To open up the sealed door, you'll need to punch your way through the boarded up door where you'll find some more biomass and a fuel dispenser. If you don't have any fuel for your flamethrower, grab some and use it to burn away the biomass blocking the door next to you (you can always grab some more once you're done to clear the blocked door outside).
Inside this room you'll find a Traveller's Seal on a bench with a message saying you can use it to open rooms sealed by previous Travellers. These are single use only so you can use it on the locked door outside, or save it for later.
Whatever you choose here, there are more to find as you explore. I can't say whether there's a Traveller's Seal for every locked door, or if you'll have to make some choices for which doors you open along the way, but it's generally always worth opening them as there's consistently useful supplies inside. If you're not planning on using one immediately, it's worth stashing it away when you can as it'll take up precious inventory space otherwise.
If you want help elsewhere, then my Cronos tips cover a wide range of things you'll probably want to know about to stay alive in this challenging survival horror.
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