After reaching Prideholme, you might make a guild by opening the guild screen with ALT+U.
This will cost 2000 silver, but you should have plenty to spend after completing the prologue.
To leave a guild, simply head to the guild screen using ALT+U and pick the Leave Guild option.

Guilds can progress all the way to level 25, which allows you to have 100 player slots.
100 players is the maximum guild size in Lost Ark.
To increase your guild level, you oughta complete weekly quests for your guild.

What are weekly guild quests in Lost Ark?
Weekly guild quests are tasks that the guild leader can set.
As you complete these quests, you’ll earn guild XP and other rewards, like Bloodstones.
Bloodstones are a currency that you’ve got the option to earn by contributing to the guild.
This guild treasury is then distributed between all guild members, allowing everyone to share the profits.
That’s everything you better know about Lost Ark guilds.