2 hours ago, Amicus Draconis said:You're welcome and thanks!
Thr´or's Map came to my mind as well and Map of Rhovanion, but your idea sounds good: It will effectively be +1 Willpower, when you have travelled in the previous round. A cost of 0 might be a bit on the cheap side for a hitpoint and one point of willpower, but on the other hand there probably will not be a location to travel to each round.
Playtesting will help here for sure. And do not forget, this version of HoG could also make Sneak Attack for free, as if this event was not powerful enough already.
You have a point here, the only problem I see, is that dwarf mining is found mostly in tactics and spirit, with the exception of Soldier of Erebor and Ered Nimrais Prospector, so Leadership might not be the best choice for a sphere.
For 0 cost, I'd probably want the boots to not stack with each other. And dale does note that the active location is the least useful place to put it. My feelings are that the Boots were on the edge of viability before, and so this might be enough to push them over, but I think that's a playtesting discussion.
Just a note, HoG won't interact with Sneak Attack, as that ally is not discarded. Returning an ally to hand will not trigger the horn. (it's the reason it doesn't work with Silvans either)
In Leadership, there is also King Under the Mountain, A Very Good Tale, and To Me O My Kinsfolk (which isn't a mining card exactly, but temporarily gets you allies back that got mined away - it's actually really good with things like Soldier of Erebor). But it is a valid note.