Going back to the start of the original Old School RuneScape (OSRS) days, long before OSRS actually became OSRS in 2013, quest difficulty has always been a fun point of discussion among the community.
Some quests are quite a bit easier than their difficulty ratings make them seem, while others could probably be upgraded to the next tier due to the challenges they present.
Which quests fit the latter? Here are five we believe are underrated from a difficulty standpoint.
No. 1 - Sins of the Father
The main reason why the Sins of the Father quest is not listed as a Grandmaster quest was always believed to be because the developers want to saved that distinction for the final quest in the Myreque series.
And if that quest, recently revealed as The Blood Moon Rises for early 2026, is more challenging than this one, that status will absolutely have been earned.
Why? Because Sins of the Father itself should be listed as Grandmaster, hands down. And that's without a battle against Lowerniel Drakan himself.
Like any good Grandmaster quest, this one has a compelling storyline from start to finish, plus a number of boss fights leading up to the main fight. And the main fight is a doozy.
The fight with Vanstrom Klause is one of the most unique fights in the game, quest or not, and it requires constant focus and pinpoint accurate clicks throughout to master the mechanics. Even with experience, a victory is no sure thing.
I would personally rank Vanstrom as a harder boss than the main bosses in While Guthix Sleeps (Balance Elemental), Monkey Madness II (Glough), Song of the Elves (Fragment of Seren), and possibly even Dragon Slayer II (Vorkath and Galvek), based on my own experience with each of them.
Those are four of the five Grandmaster quests, and you could make a strong case that Vanstrom would rival a couple of the Desert Treasure II bosses as well (yes, in addition to the obvious fact that he is unequivocally tougher than Duke Sucellus).
Regarding the boss fight, it would be nice if this were a replayable encounter, though it sort of already is via Quest Speedrunning mode, provided you spend the time and effort to do the entire quest each time.