Needed

Tells your game how to show a hit on you in detail, for example being knocked back or staggered.

Sends a chat message that you typed.

The server tells your game that your request to respawn did not work.

The server sends your game the death recap, the summary of what killed you shown after you die.

Keeps track of the game events that are active (such as seasonal events) and which daily event bonuses you already used.

Keeps track of which game modes you are queued for or playing, and the matchmaking state for them.

Keeps the shared world map information in sync: the data behind what the world map shows that is the same for everyone.

Keeps your group information up to date: which group and raid you are in, your Group Finder listing and applications, and the invites you sent and received.

Keeps your company information up to date on your screen: which company you are in, your rank and the company details.

Keeps your quest list in sync: what you tracked, what you completed, what is active and how each task is going.

Keeps your expedition status in sync: whether you are in one, whether you are queued, your cooldowns and how many you ran lately.

Keeps track of an invite you sent or received, like who it is for, what it is for and when it runs out.

Probably a points counter with a maximum that resets after some time. We do not know what it is for.

Keeps your season progress in sync: your XP in each season and which rewards you already claimed.

Keeps the counters your season tasks use, like how many creatures you defeated.

Keeps track of what your abilities are doing in a fight: which abilities you used, which hits you took or landed and which actions are still running.

Your list of achievements and how far along each one is.

The state of a built structure such as a crafting station, a camp or a town building: whether it is built or upgrading, what materials were added, who owns the territory and whether it is ruined.

Your camp information: which camp you currently have, which skin it uses, whether it is being attacked and how long until you can bind to a camp again.

How charged up your attack or weapon is, as a percentage.

Your list of muted chat entries (people or channels you or the game have silenced).

Keeps track of your crafting cooldowns and the gear score bonuses your crafting gives.

Keeps your fishing state in sync: whether you are fishing, the line tension and what is on the hook.

Keeps your shared storage in sync: the items in it, how many are over the limit, the total weight and how many slots each town has.

Marks whether a character is knocked down and cannot act, so other players see them lying there.

Keeps in sync whether an object in the world can be used, whether someone is using it and its cooldowns.

Keeps in sync which object your character is using right now and whether it is allowed to use things.

Keeps your item skins and dye colors in sync, so the game knows how your gear should look.

Keeps your spell casting state in sync, including whether you are holding a channeled spell.

Keeps track of what a quest NPC or board is offering, including missions, goals and when they expire.

Keeps track of who owns a structure: the company, the owner, the crest, the access rules and the faction.

Probably tells your game that something in the way is stopping you from finishing placing an object, like furniture or a camp.

Keeps your list of home points (places you can respawn at) and which one is active in sync.

Keeps your housing status in sync: whether you bought a house, which ones you own, and whether you are standing on a housing plot.

Probably keeps track of whether your name tag shows or hides your level to other players.

Probably keeps count of how long your character has been played in the current session.

Probably keeps track of progression points you have earned in different pools and how many you have spent.

Keeps track of arrows, spells and other thrown or shot things in flight: where they start, how fast they fly and what they hit.

Keeps your reward track in sync: your rank and the rewards you can pick from.

Probably keeps track of the scripted parts of the world, like objects and creatures that appear during an event.

Keeps track of spells and projectiles in the world, such as where they start, where they fly and who cast them.

Keeps track of a temporary team or side a player belongs to, such as during a war or an event.

Keeps track of how many buy and sell orders you have in the trading post, overall and by category.

Keeps track of your appearances (transmog skins): which ones you own, which ones you have captured from items and which are ready to use.

Keeps track of the war schedule, changes to it and the influence races, the contests for control of territories.