I'm jonesing for these tower defense games. The first edition was released by Robot Entertainment in 2011, Orcs Must Die 2 came out in 2012, OMD Unchained (online multi-player) was from 2014 and OMD 3 was from 2020/2021. They're all great fun and I am sad that we may never get an OMD 4. Game 1 was single-player, 2 and 3 had coop mode too.
I toyed with the idea of creating a community here for the games, but I'm not sure there are enough fans / enough things to talk about now.
For now, here's an awesome slide show from Unchained, for any fans: https://de.ign.com/orcs-must-die-unchained-ps4/112585/gallery/embed
OMD is a fantastic series! I remember playing the first one back on the 360, and then being sad because I didn't have a PC to play 2 when it came out. When I eventually got a PC I sunk so many hours into the series. I'm also quite sad the series is probably over because there really isn't anything else that fills that space. I've tried Sanctum but it's just not for me.