Easiest and fastest Rune farming location in ER is the ball in the Lenne's Rise, top right corner of the map.

This will reward you 2000 (1952) Runes every 15 seconds.

Location

1. Go to the Third Church of Marika. It's in the right of where you spawn outside in the early game area.

2. Go behind the building to find a portal and use it to travel to another location.

3. Go down until you are on a big bridge with a dragon boss on it.

4. Go past the bridge and immediately go down the road in your left.

5. Go down and save the game in the bone fire.

How to farm Rune

1. Summon and mount up your Torrent (horse) and go down the road under the bridge.

2. A ball will follow you, immediately jump down and jump back up so the ball falls down to your right.

3. You can also not jump down if you are fast enough, jumping is just the easier way if you know how to use your horse's double jump.