Edited 22 June 2021: Loremaster achievement glitch fixed by 21 June 2021 patch
. Whereas, as of this edit, players are now unlocking the achievement, it appears you now have to discover all 195 lorestones rather than the 175 required when the game was initially released
. Comments are welcome and will be appreciated by people who got caught up in the achievement glitch.
Caution--potential glitch: Edit as of 21 April 2021: As of this writing, the most recent unlock was 8 April. Players have reported issues with the achievement tracker getting stuck and the achievement not unlocking. I have submitted a trouble ticket to THQ Nordic and will revise this solution should there be any changes. It is very important to use the achievement tracker. Especially if it gets stuck but also if it does not, make an insurance save before you discover the 175th lorestone. If the achievement fails to unlock, you can use this insurance save later when a patch is issued to resolve the problem.
The achievement originally unlocked when you activate the 175th lorestone out of 195 available though the achievement description says you must discover 'all' lorestones. Following the 21 June 2021 patch, all 195 lorestones must be discovered for the achievement to unlock. @Asturgis
provides the following insight in the comments: If you discovered all 195 lorestones during a time when the achievement was glitched, revert to a save before you found all 195 stones and 'rediscover' the final lorestones. Once you rediscover the 195th lorestone, the achievement should unlock.
Lorestones appear on the mini- and local maps when your detect hidden skill is level 10. Since this is the most time consuming achievement in the game, it is worthwhile to max out your detect hidden skill as soon as possible. Since you cannot advance to level 8 by investing a level-up skill point until your overall level is 16, a good approach is to use a fateweaver. Play the game until you reach level 16 and invest in the skills as you see fit.
At level 16, go see a fateweaver and reset your points. First, bring your detect hidden skill to level 10 and apply the rest of your points as you see fit. When you continue playing the game, all lorestones will be the most prominent feature on your mini- and local maps identified by bright blue dots. You can then activate them as you come across them without going much out of your way.
The walkthrough shows all lorestones on the map. The ones on the world map are shown by region and sub-region with special maps for the lorestones in dungeons. Even if you are not using the walkthrough, you might want to consult the special lorestones page to assist you: Kingdoms of Amalur: Re-Reckoning Walkthrough
The very short video below, created before the 21 June 2021 patch, shows the 174th and 175th stones being activated. Note the bright blue dots on the mini-map. The achievement unlocks, after a short lag, when the 175th stone is activated. Following the 21 June 2022 patch, the achievement will pop in similar fashion when the 195th lorestone is discovered.