Elden Ring is one of the Elden Ring.
The brainchild of modding icon 'Zullie the Witch' and her colleague 'Dropoff', you can now scatter random Armored Cores around The Lands Between. Why? I have no idea, but am I going to do it? Absolutely.
Unfortunately, you can't play as an Armored Core or fight one, but given they're pretty small (10m tall, apparently) when compared to a Fire Giant (24m), maybe it's better just playing as The Tarnished. Instead, they stand still, like ominous telephone poles; robotic bastions of a bygone fantasy era, watching over The Lands Between as silent, mechanical, sentinels.

During their datamining adventures, Zullie and Dropoff also found an Armored Core test mech, that looks like it's walked straight out of Minecraft. "I ended up finding this test model and it amuses me a lot," they write. "There are some variants with different legs, so it may have been a dummy for setting up the animation sets for different styles."
At the moment there's a distinct lack of Armored Core 6-inspired mods for Elden Ring, but I doubt it'll stay that way. Or, maybe, just maybe, we'll see Elden Ring infiltrate Armored Core 6 and transform your mech into Radahn instead – he's 8m to the Armored Core's 10, so they're relatively even in size. Modders, get on it.
If you're yet to explore the vast expanses of Rubicon, then I suggest checking out our Elden Ring classes to help you topple some Fire Giants.