Recently a message from a discord bot appeared from a mutual server I was in. The message came from the bot username Nexus#5481 (Discord ID 777234996481097748) and seemed to link nothing related to the bot itself.
Here is the message, nothing that seems to dangerous except both the links point to only being able to invite the bot to my own server. No website, and a google search pulls up nothing.

So what could this bot be up too?
It has 3 commands:
- n!grow - Grow your server.
- n!invite - Gets an invite link of the bot.
- n!help - Shows this message.
The fact that this bot only sends out messages to invite the bot, and the commands are a total of creating an invite link for the bot and a 'grow' command which I assume just spams more invites suggests to me that this is a data collection bot.
A data collection bot (or a farm bot) is used to gather information on as many users as possible, with its goal being to grab username details for future spam advertisements which will be sold. This kind of data collect is against Discords TOS and is highly unethical.
The bot could also contain code which activates based on the rights it asks for. The Nexus#5481 bot is using the Administator right which will grant it full access to the server. It will be able to take control of the server, delete it, or any other action the bot owner wishes to perform.

In the past bots have been made to Direct message every user of a discord saying 'join this new discord' and then deleting the current one once completed. This is technique used to grow servers for later sale.
Be extremely careful when dealing with this bot. With no obvious infomation out about its owners or its goal, or what it does while requireing Administrator rights it will likely do some very questional actions.