A map pin can send you in circles during Across the Threshold, which is why plenty of players assume the quest is bugged. It usually is not. You are looking for a live Realmwalker event, not a fixed entrance. While levelling, keep an eye on Helltides and seasonal Ruptures, pick up gear as you go, and do not burn materials on throwaway pieces. Even Diablo 4 runes are better saved for the point where your build has stopped changing every other level.
Getting Through the Quest Without Wasting an Evening
The cleanest route is the Colossal Rupture in the Fields of Desecration near Zarbinzet. Surging Ruptures inside Helltide can lead to a Realmwalker too, but they are not dependable when you are trying to finish one specific objective. Stay around the ritual area, kill the waves, close what needs closing, then deal with the Realmwalker. Once it drops, use the portal straight away. That takes you into a Deathtoll Chamber, where the fight is a bit more than a simple sprint to the boss. Watch for Gravehound orbs moving toward the Exarch. Letting them through makes the room harder than it needs to be.
What Should Actually Be On Your Seasonal Checklist
Clear Ruptures during Helltide when they appear naturally
Use Colossal Ruptures when you need a guaranteed Realmwalker route
Run Deathtoll Chambers for Superior Lair Keys
Save keys, then farm the Corrupted Reaper in batches
That order matters because each activity feeds the next one. Players often spend too long roaming the open world after they have enough power for Torment content. It feels productive because monsters are dying, but it does not always move the seasonal loop forward. Ruptures lead to Realmwalkers. Realmwalkers open Chambers. Chambers bring in keys, and keys give you runs at the Corrupted Reaper. At higher Torment levels, the Chamber key rewards become more reliable, so move up only when your clears still feel quick. A slower tier with repeated deaths is not progress. It is just more loading screens.
Pandemonium Fragments are where the chase gets serious. The Reaper can drop them, and the repeatable Glints of Hope reward adds another steady source. Four Fragments can upgrade a Unique into a Mythic through the Cube, but the result is random within that item slot. So do not throw in the first Unique you find. Wait until your build is settled and the slot genuinely needs help. If you are short on materials or simply want to avoid a bad craft at the wrong time, comparing options such as the best place to buy diablo 4 runes can help you plan around your build instead of gambling away a useful base item.