expressions
your server's emoji, stickers and sounds, in tools → expressions: add them, copy them to your other servers, and keep them for later.
add some
drop pictures or sounds on the page and arii makes them fit. you can also add one from a link, or bring some in from any server you share with arii, even ones you don't manage: animated ones and other servers' work without nitro.
keep them for later
your collection keeps expressions you like, to take to any server you manage. put a few in a pack to share with a link anyone can keep a copy from.
from discord
/steal takes emoji and stickers from a message straight into your server; right-click a message for the same.