Stormhold is a low level dungeon (level 20 or so) in Antonica. When you are significantly higher level than the zone, i would recommend 50+, you can mentor down to 20 or 25 and go here to farm for plat. There are quite a lot of nameds and collections that you can farm here for small amounts of plat. The big seller here though is the Sword of Thunder, the sword drops from any mob within the zone with anything from 0,2 to 0,8% drop rate so it’s pretty easy to acquire. The sword drop from both bodies and chests so be sure to not just loot the chests. The sword is used to get the quest for Berik. Sword of Thunder that is later used in the Heritage quest to get the Electrified Bone Bladed Claymore.
You can farm the sword anywhere in the zone, so just start up top and work your way down. The sword is a lore item so you can only have one on you, so when you get the sword head back and put it on the broker. Depending on your server it can fetch upwards 50 plat.