Access mohgwyn palace through varre's questline early, or use the consecrated snowfield portal later. The palace approach ledge-road grace point is your primary farming spot where you've got two solid options. First method: shoot the giant crow below with any bow, making it fall for quick 11k runes. Second method requires the sacred relic sword from the final boss, but it's worth the wait - use wave of gold on the albinauric groups for 50k runes per run.

For maximum efficiency, equip golden scarab talisman and pop a gold-pickled fowl foot, they stack nicely for 50% more runes. Just rest at the grace point to reset and repeat. The albinauric method is significantly faster but you'll need endgame progression, while the bird strategy works great as an earlier alternative.

Tip: sacred relic sword method still works perfectly after updates, and those albinaurics aren't going anywhere.