The achievement unlocks when you play the entire main story line on hard difficulty. It will not pop immediately following the final battle. There are some final cut scenes first that you can skip and the credits that you can also skip. You end up in a new safe house called Orbocant
in Rathir – Upper City
. If this is your first playthrough, you will unlock:
After a few moments, Agarth will come in to talk to you. It is at around this point that the achievement will pop as shown in the below video:
The final battle can be simplified if you know its structure beforehand. It is not a conventional fight. You can only damage the boss in a very short window after you invoke reckoning mode. Your gauge is empty when you confront the boss. The game provides enemies, "Splinters of Fate" for you to fight in order to charge your gauge.
However, if you bring several potions of fate, you can charge the gauge with the potion. Do so, as soon as the boss stops talking. If you use some potion buffs and an overpowered weapon as shown in the video, you can deplete over half the boss's health in one go. Use another potion of fate and refresh your offensive buffs. Again, invoke reckoning mode and attack the boss immediately after that. In the video, this second round was sufficient to completely zero out the boss's health. However, that was because a top of the line Primal Sword was used. More realistically, it will take a third round.
When you reduce the boss's health to zero, you'll see a dimmed
prompt. Run up to the boss and the prompt will become bright. Press
to deliver the coup de grace. If you fail to act quickly, the boss will recover some health and you'll have to invoke reckoning mode an additional time and respond, again (a little more quickly) to the button prompt.
Watch the end cut scenes and credit (or skip them). The achievement will pop around the time Agarth makes his appearance in post-game mode.
Hard difficulty is more intimidating than it sounds. The game provides a decent learning curve. You can use reckoning mode in almost all major boss confrontations considerably reducing their challenge. If you are having difficulty, try using a different weapon combination. I recommend using the hybrid Finesse/Sorcerer destiny and using Chakrams and daggers as primary secondary weapons with longbow as a fallback when I need greater range.
Chakrams are a mid-range weapon with a curved trajectory providing you with an umbrella of protection. They specialize in crowd control. When you face a single target, super-fast daggers keep it off balance. The Finesse/Sorcerer hybrid destiny replaces the normal dodge with a short teleport. You can teleport through enemies, poisoning them at the same time. This both damages them and slows them down.
Naturally, all destinies have their strong points and much is personal preference. I suggest this only to those who may want an alternative. Being able to attack with lethal weaponry from a stand-off distance while having exceptional evasion considerably lessens the challenge of playing on Hard or Very Hard difficulties.