The level design of Dark Souls 2 is as much a highlight as it is for the rest of the series. However, not all areas throughout Drangleic are equally beloved, especially those that come from the DLC areas or have been reintroduced in the Scholar of the First Sin edition. This is most notably seen in the fight against Lud and Zallen, the King's Pets, which comes from a series of areas designed around Dark Souls 2's cooperative multiplayer.
One aspect of the Lud and Zallen fight that makes this encounter unique among FromSoftware boss designs is that the lead-up isn't a controversial design that divides fans. Instead, this is almost unanimously maligned by Dark Souls 2 fans, with very few players actively advocating for the bosses or the Frigid Outskirts that they can be found in.

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Lud and Zallen Enhance the Duo Design in a Frigid Wasteland
Exploring the Frigid Outskirts
As is the case in-game, the first thing to explore about Lud and Zallen is the Frigid Outskirts location that the two bosses wait within. Included as a part of the Crown of the Ivory King DLC, the Frigid Outskirts are a long walk from the start of the area with no bonfires on the way to the boss arena. Only broken up by a handful of ruins, the location is little more than an expanse of snow, with a blizzard that rushes through to obscure visibility for any player unlucky enough to be caught in it.
To pile on with the constant snowstorm, the Frigid Outskirts also include Frozen Reindeer enemies, which will appear from seemingly nowhere and charge directly at the player. The result is an incredibly difficult section that feels unfair in a way that doesn't really fit with the tough-but-fair defense that most fans fall behind when discussing FromSoftware's difficulty. What makes this entire situation worse is that the Frigid Outskirts need to be traversed every time the player wants to challenge Lud and Zallen with absolutely no shortcuts to make retrying the boss more manageable after dying one or more times.
Lud and Zallen's Double-Team Fake-Out
By the time players find Lud and Zallen, players will have already faced off against Aava, the King's Pet, who fights the same as the duo boss. So, when Lud is the first of the two to appear, it might seem like an odd reuse of a previous Dark Souls 2 boss. However, as the player brings Lud down to about half-health, the second giant tiger approaches and adds a secondary level of pressure to the fight. It's a twist that FromSoftware would bring out again in later games, like with the Crucible Knight and Misbegotten encounter in Elden Ring.
The fake-out is a vicious turn in what should be the second half of the fight but almost restarts the fight entirely with the added difficulty of having to keep track of two enemies at a time. Given that both Lud and Zallen can also fire spells from a distance, even letting one of the two take a more passive stance doesn't remove the pressure of having both on the field at once.
It's an escalation that keeps Lud and Zallen from feeling like too much of a retread of the Aava fight but doesn't necessarily drop the quality to the worst bosses Dark Souls 2 has to offer.
The escalating difficulty doesn't even end with the addition of a secondary boss, as whichever of the two is the last remaining alive will begin to slowly regain health until the fight finally ends. It is an intensely tough formula for a boss that would normally be a highlight for any FromSoftware experience, held back almost entirely by the design of the Frigid Outskirts. However, this does still act as a strong cautionary tale for the developer and anyone else in the Soulslike genre to keep in mind when designing around punishing difficulty.