It drops from duty: Aglaia. Aglaia is a level 90 raid introduced in patch 6.1 with Endwalker. It is the first part of Myths of the Realm.
Nald’thal chest contains Aglaia Coin (Drops at a fixed rate).
Completion Reward: Upon completing Aglaia, players can also earn a separate reward once per week: two Cracked Anthoclusters and one Aglaia Coin. The Aglaia Coin can be exchanged with Nesvaaz in Radz-at-Han (X:10.6 Y:10.0) for items used to enhance equipment purchased with Allagan Tomestone of Astronomy.
Aglaia Coins are exchanged with Nesvaaz in Radz-at-Han (X:10.6 Y:10.0) for items used to enhance equipment purchased with Allagan Tomestone of Astronomy.