A Colossal Problem

Event: A Colossal Problem is an event quest in the Fallout 76 update The Legendary Run.

Walkthrough
As soon as a nuke is dropped on the mine, the thirty minutes event timer starts. One can join the event and subsequently gets teleported into the mine's interior. From there, one has roughly five minutes of time to prepare for the fight.
 * Stage 1 - Time to get ready

It is possible to repair, modify or craft equipment since many workbenches are conveniently placed both at the entrance and in the large cavern after the tunnels. Several notes and a holodisk can be found with a little exploration and a total of three wendigo spawns can be killed for leisure.

After the time has passed, the rubble on the right-hand side of the large cavern will collapse, allowing for further descend into the mine.

After dropping down the now accessible mine shaft, one is tasked to investigate the noise, only to find Earle Williams, who has transformed into a hideous wendigo colossus. He has a rather large amount of health and will mutate once his health is low enough.
 * Stage 2 - The epic fight

The fight itself consists of placing explosives into the meat piles around the cavern, getting feared (a lot...), killing off the waves of wendigo spawns that Earle attracts, evading the goo that Earle's heads are spitting and evading the burning embers that drop down from the cave's ceiling during the later stage of the fight.

Other than that, it is just a plain damage race against time, much like a fight against the scorchbeast queen, but with more to look out for during the fight.

Dying during the fight results in respawning in the large cavern with the previously blocked mine shaft, dropping down said shaft again allows for a quick return to the action.

After Earle has been defeated, the mine will finally start collapsing, giving a two minute window to make the escape.
 * Stage 3 - The great escape

Relieving Earle of any items he possesed is recommended before heading up the sloped tunnel in an orderly fashion, killing any wendigo spawns on the way out.

Exiting the mine will conclude the quest, awarding experience and loot as usual.

If Something Sentimental is still an active quest, Earle's pocket watch will be found on his remains, allowing the quest to progress further.

Behind the scenes
Victoria McCreary was the main quest designer for the event.