While Pokemon Legends: Arceus isn't open-world, it is more open-ended than most other Pokemon games. Players are generally free to tackle the game's objectives, outside the story, whenever they want to. The Pokedex is something that players can tackle at any time, with some exceptions. Players will need to progress to certain ranks on the Pokedex to be allowed access to the next area. However, one Pokemon Legends: Arceus player took that open-ended objective to the extreme in the first area of the game.
The Pokedex in Pokemon Legends: Arceus behaves differently than Pokedexes in other Pokemon games. In previous games, simply catching a Pokemon or evolving it was enough to fill out its Pokedex entry. In Pokemon Legends: Arceus, there are various tasks players need to accomplish in order to fill in the Pokemon's respective entry. These can range from catching more of that Pokemon, seeing them use certain moves, feeding them food, etc. These tasks will help you rank up by earning you points towards Pokedex completion.
Funny Pokemon Legends: Arceus Clip Shows Socially Awkward Spheal
There are 10 ranks in Pokemon Legends: Arceus, and the player is expected to hit level 2 before leaving the first area, the Obsidian Fieldlands. However, Reddit user Kyarmak shared a screenshot that showed that they have hit Star Rank 9 without leaving the Obsidian Fieldlands. To accomplish this, it is likely they would have had to capture every single variety of Pokemon there, including the ones from the space-time distortions, raised them, evolved them, and completed entries from the evolved forms' entries too.
There are a number of rare Pokemon like Munchlax and Happiny that can appear in the Obsidian Fieldlands, but their appearance rates are
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