If you want to make something to keep a Runelord safe...
just make Runic armor. It has the tremendous advantage of
not taking up an entire Master Rune slot.
If you want a giant, walking siege engine... make a Rune Golem.
Don't mix the two, because, and here's the other problem with making something like a mecha suit:
Dwarfs have never piloted giant robots, which means this is an entirely new form of warfare to them. (If you want Dwarfs to explore and pioneer piloted warmachines, it's probably better to start with a more conventional warmachine than a golem.)
Forget arguments like "We'd have to teach other Runesmiths how to make Golem Armor", which get argued back with "Well, we just saw two Runesmiths make Rune Golems for defense of the hold." Because just
using it, even if a Runesmith can make, is going to require even
more specialized and rare knowledge.
In other words: why would Runelords want Golem Armor, when they can have Armor instead, which still has room for a Master Rune?
Leaving only a single rune slot for use making it good at being a big face smashing golem. So faced with this issue I thought to myself "Well people are going to want to do sapient golem shenanigans because of giant robot ideas soooo what do? Ah Rune of Fortitude, something interesting might happen and if it doesn't oh well it's still tough and good with the Heart". Put another way, even if the Rune of Fortitude makes doesn't make it sapient, it makes it a better golem, especially with the Heart.
Well, there's also the Rune of Stone. Provides more armor, kin to Dwarfs. Though Fortitude specifically was called out as "You can make a really good Rune of Fortitude with this thing!" so. On the other hand, maybe both Fortitude and Stone? Together, that gets you
"Eternal, ever-enduring stone."
Shame to lose "Mighty" though, yeah... ((I mean on the one hand, you could say that if it's going to be a Giant Robot, then it's going to be really strong anyway. On the other hand, you could say that about its toughness and armor too, and we're talking about Fortitude and Stone runes, so.))
...
I think one major reason I really like the idea of making a Rune Golem from this?
Is because, given the fluff description of the Greedy Heart... it sounds a lot like it would result in a Golem that potentially won't ever need to go into slumber! Where other Golems would need to be "awakened"... this one will never sleep.
Imagine that. It will always be available for the Dawi.
... God, do I want to make it able to
breath fire too...
There's another possibility if we can leverage the Rune of Brotherhood. Put that on the golem and then link it to a helmet or some other piece of gear that a dwarf wears. As a result the golem can use the dwarf's skill at combat/take more direct orders making it a better fighter. And when the fight's over simply direct the thing back home and take off the helmet. Gets a similar effect without the pitfalls of dealing with a sentient golem.
Actually what this sounds like is some kind of "Control Rod" arcane item! Or a "helm/circlet/crown of control."
A control rod or crown that controls a Rune Golem. That...
feels like the sort of magic item that would exist, especially in relation to a golem, no? Though... any form of control item runs the obvious narrative risk of... well... the fact that you set up a way to get control of the golem.
... Maybe make it a weapon instead? That would be cool! Something like
Brotherhood + Rune of Skill + Rune of Skill, and given to the Longbeard Champion of the Throng.
I sorta like that idea. Just... you want a golem to fight really well? Then, you pair it with your army's Champion or herald!
