So how does Neeko, Blending In actually work? When do I choose the legends, do I get three legends per Neeko in my deck, can I add multiple of the same legend to the Legend Zone, do the legends enter ready, and do I need to reveal them to my opponent?
You choose the legends during deck building-at competitive OPL, you must register those legends as part of your deck list, and you can store them with your sideboard. The 3 legends are shared by all Neekos in your deck. You cannot add multiple of the same legend to the Legend Zone. The legends enter ready. You do not need to reveal them to your opponent until they are added to the Legend Zone.
Let's break down Neeko's rules text. If your deck (Main Deck or sideboard) has one or more copies of Neeko, Blending In, you pick three legends in addition to your starting Champion Legend. Those 3 legends must be different from each other and from your Champion Legend. Regardless of how many copies of Neeko you have in your deck, you will choose three legends in this way.
When Neeko's play effect resolves, its controller picks one of the legends chosen during deck building and adds it to their Legend Zone alongside their Champion Legend for as long as Neeko is on the board. If Neeko leaves the board, that legend will also cease to exist. The legends don't exist in any zone of the game while they're not in the Legend Zone; they don't exist at all. That being said, if one or more of those legends are already on the board, a player can't choose to create additional versions of those legends; they can have at most one legend on the board per legend chosen during deckbuilding. If somehow a player played a fourth Neeko, they would fail to add a legend to their legend zone.
The legends added this way are not tokens. They are legend cards and behave in all ways like normal legends do. If an effect instructs a player to "ready a friendly legend" they can target and ready any legends controlled by them or an ally. If an effect instructs a player to ready "your legend," that refers to any legend controlled by that player. Such an effect does not target a legend; the legend is chosen as the spell or ability resolves.
Relevant rules: 103.1., 440.2.a., 440.3.b., 440.3.c., 355.10.g.
