Hi, I recently switched from Alliance to Horde for something different. I’m looking to join a RP guild that’s pro-Sylvanas/Undead centric. I don’t get to play that much at present, but I’m an experienced role player, a pretty good PvPer, and generally an easy person to get along with, I just don’t know many Horde players and I’d like to be able to engage in some RP.
Let me know if your guild fits the criteria I’m looking for and you’re recruiting. Thanks!
Hey there! Welcome to the Horde 
Here’s the link to the promo thread for the guild that I’m in, Caravan of Wonders. There’s also the thread for listing all the Horde side guilds, rp and content guilds, as well as the guild expo. I hope you enjoy your stay!
https://us.forums.blizzard.com/en/wow/t/comprehensive-guide-to-moon-guard-horde-guilds/106070/31
I also suggest that Hand of Vengeance may be suitable for your needs:
Hello there and welcome to glorious undeath!
Here is a little excerpt from our FAQ:
Who are we?
The Onyx Rose is a Heavy RP, Horde guild based out of the Plaguelands. We offer IC or OOC events weekly in addition to open RP almost all the time at our Headquarters at Tyr’s Hand (proxy location). We welcome new RPers who are willing to learn as well as long time RPers, and anyone interested in a differently themed guild.
Does the Onyx Rose have a theme?
Yes, we absolutely do. The Onyx Rose is an undead, dark-themed Order allied with Warchief Sylvanas Windrunner and her Forsaken. While not a Forsaken only order by any means, we do have a large population of undead, death knights, and others along with our living. The Rose walks a fine balance between its living and undead population, and its leaders work hard to keep the peace.
We conduct regular operations in the surrounding territories against the Alliance, and maintain a large military presence on the Forsaken Front. We aid our allies in holding the line. New members will find themselves in a bit of a surreal environment of living and dead meshed together as one big twisted family. The shell of the person is less important to us than the personality inside, so long as they are loyal to the “family.”
What time are you active?
Generally our events are scheduled around 7:00-10:00 PM Moon Guard time (about 8:00-11:00 PM for the East Coast US, and 5:00-8:00 PM for West Coast US). However, at least a few players are logged in throughout the day, both in game and in discord.
Will I need anything to join?
Yes. As a guild, we require Discord. It is an excellent tool we use to communicate for everything and as a member you will need it. We will never force you to use voice to speak with us, but you will be required to at least be able to listen, especially in raids and guild meetings. This is also our primary means for passing down information and communicating with our members when not logged in to World of Warcraft itself.
We also require TRP 3 as your RP addon. The entire guild uses the program for more than just our profiles. TRP 3+ Extended allows us to create items and books to use in our RP, and even quests for characters to play. Having the base TRP 3 addon allows you to fully participate in guild events.**
And feel free to contact me in game via whisper or mail, I’m happy to help!