I was trying to think of ways that the sense of magic in the world of H&H could be increased, while maintaining subtlety, and I got to thinking about curses. Not overt magic to be wielded in combat with flashy effects and pretty lights, but obscure forces of nature and divine retribution that may in some cases be called down upon others, but generally are self-incurred through one's own misdeeds.
Curses could have a percentage chance of being inflicted on a hearthling as a result of any number of actions that might catch the attention of the gods' sense of injustice or Nature's sense of balance. Murder and desecration of graves might carry a nigh-certainty of being cursed (~90% maybe?), with vandalism being significantly lower, followed by theft and finally trespassing which may sit at a measly 1%. Any number of actions not taking place on claimed land or in combat, like taking a boat you didn't build, harvesting crops you didn't plant, or killing a particularly majestic animal (one with stats above some unknown threshold), might direct divine ire your way.
Of course, curses are no fun without variety. They would obviously vary in severity and perhaps be loosely separated into classes for different magnitudes of crimes (though the gods do sometimes have a disproportionate sense of punishment...). Most curses would be accompanied by a method of atonement, with many requiring a small act of penitence, some needing significant material sacrifice, and a handful being permanent. Someone who finds themselves under the Curse of the Wandering Man, for example, would not be able to step upon claimed land or claim land for themselves until they wash themselves clean in a river. The Curse of the Greedy would incur a 50% chance that any item they pick up turns to ash in their inventory, alleviated by dropping something equipped to their person into water for somebody else to have. The Hunter's Folly would disguise aggressive animals as rabbits and squirrels in the eyes of the afflicted until they feed a clover to a horse. The most severe and immediate, carrying a high chance of death and guarantee of disfigurement and permanent stat penalties, would be the Smite, in which the offender is struck by lightning and briefly immolated. The list of curses could go on, with all sorts of fun effects and means of alleviation.
So that we don't have people running around dunking themselves in rivers and dropping their gear in the watery depths in a frantic scramble to clear themselves of an unknown affliction, maybe a little pop-up box listing the curse (or curses) they're under could appear upon studying a Mirkwood Offering. The curses could each have a nice bit of lore text that cryptically hints at its effect and method of resolution.
As with variety, curses are also no fun if you can't inflict them on other people. This mechanic would take the form of talismans worn about the neck or wrist, or hung from the horns of a claim statue, and guarantee a curse upon the unfortunate one who attacks the bearer or invades their claim. Upon creation, they would be able to have conditions set for their activation from the formal list of crimes in the game, so that an errant newbie (or alt) trespassing would not necessarily set off the talisman and waste it on an unintended target. They would be crafted at an altar with varying levels of sacrifice needed for the level of effect you want (though this would still have an element of randomness due to divine fickleness, as stated above), and the person crafting it would have no idea what curse might be attached to the talisman.