The method I’m currently using to work towards the Feat of Strength is as follows…
- Have a main hero capable of speed-farming
- Collect Puzzle Rings (drops, gamble at Kadala, upgrade rare to legendary in Cube, etc)
- Level a Gem of Ease to rank 25
- Obtain a level 70 legendary dagger (this is because all classes can use one)
- Use the Cube’s recipe to remove the level requirement of an item on the dagger which uses up the level 25 Gem of Ease created earlier (this is important, i.e. do not socket it into a dagger - you do NOT want the +XP gain from kills)
- Create an alt of the class whose ethereals you need
- Give the level requirement removed dagger to the alt
- Go to an open map, kill enough mobs to get the alt to level 6
- Set the Cube’s armour power on the alt to Illusory Boots, so you can walk through mobs
- Create a T6 game on the alt, use a Puzzle Ring in the Cube, enter the Vault, and walk through all of the mobs (this is why we have the Illusory Boots) and enter the end boss’s chamber
- Kill Greed, and you’ll get 0-2 ethereals from the loot chest
- The kill will put the hero to around level 14-15
- Put the level requirement removed dagger back in the Stash
- Delete the alt
- Repeat steps 6-14 until you have the three ethereals for the class
- Repeat for all classes
–==[ EDIT ]==–
All done…
