The Frozen Tundra

The small settlement lies right on the southern bank of a river, which stretches perfectly straight northeast as far as you can see. You enter the town library and ask about the place.

"The area east of the settlement has been explored fairly thoroughly," explains the librarian. "Records show that, while mapping out the surroundings, explorers meticulously placed markers 1 mile apart, starting from the first marker at their base camp just 1 mile out of town and continuing due east."

"We recently managed to transcribe some copies of an explorer's notes, actually. They believed that the tundra was governed by the spirits of the hail, who would always bring explorers back to their base camp safely." She lowers her voice slightly. "Myths speak of a place where the spirits won't be able to guide you home. But no one has found it yet... and I daresay they checked pretty far."

She passes you a set of journal transcriptions. Some pages catch your eye:

...the village's groups take turns to run supplies along the markers, each building on the work of the last...

...this morning we awoke to blinding sleet all around us, save for a path directly northwest. We took this as the guidance of the spirits, and traveled in that direction until we reached the south bank of the river. There the winds suddenly changed and led us directly south. We came to another marker and spent the night by it, so we wouldn't lose our bearings...

...the sleet this morning blocked our passage westward, but again the spirits sent their guidance and led us south for half a mile. Immediately the storm shifted, and a narrow passage opened at a bearing of just more than thirty-three and a half degrees. We trekked thusward for some time, and no sooner had we reached the river's south bank than the winds changed, bringing us south again until we reached another marker, where we camped for the night...

...every morning the walls of sleet seem to direct us forward, always in one of the two directions. I have no doubt that there is a preordained path the spirits have chosen for us, and we would be foolish not to heed their guidance...

...we arrived at our base camp last night. We've made it back alive. The spirits of the hailstorm have preserved our lives, granting us their wisdom with each marker we stopped at along the way.

Your scanner pings; it appears there's a sample of ice around marker 4,849 that could be useful for timespace calibration. What should you bring with you on the journey?