There is a lack of information on chests online so here's what I know after hunting around.
- Golden chests spawn every 10 minutes form the hour in its spawn locations. There have been a few cases where the chest does not respawn on the 10-minute mark. I'm not sure if standing on the chest spawn spot blocks the chest from spawning.
- Wooden chests have a chance to spawn in one of its spawn locations. I have a few theories of when they spawn:
Has a chance to spawn every hour or every 10 minutes or every 15 minutes (really hard to keep track of it, sometimes there are times where there are no wooden chests on all channels of a map for 20-30 minutes)
Each spawn location has their own timer for when to spawn. e.g one spawn location will have a chance to spawn a chest every hour from xx:00 while another location has a chance to spawn a chest every hour from xx:10.
Each map has their own spawn time. e.g. one map may spawn a load of wooden chests at the start of the hour, another map may spawn the chests 30 minutes past the hour.
- Sometimes a lot of wooden chests will spawn, sometimes only a few.
- A gold chest will never spawn in place of a wooden and vice versa.
- I've seen wooden chests disappear in front of my eyes and I have no idea why. I have never seen a golden chest disappear unless it's refreshing it spawns at 10 minutes from the hour.
- Wooden chests spawn in locations that are easily seen. This tends to be:
Around the edges of platforms/islands/hills
At the top of tall trees or hills
Inside walls that are visible or hidden by small objects such as trees or small rocks.
Out in the open
- Golden chests spawn in various locations, both in easily seen spots and in ridiculously hard spots that require you to go behind structures. Each map has an achievement to find all the golden chests (hence why gold chests always spawn every 10 minutes). There is a guide for this here.
Common between wooden and golden chests:
A small amount of Mesos (200-250ish)
Crystal fragment (100% chance of dropping). There is a low chance of getting 10 crystals and an even lower chance of getting 100 crystals.
Rusted key (fairly common. Visit Natalie in Tria to identify it as an abandoned mine key for the treasure dungeon).
- Wooden chests can drop voucher fragments for cosmetic related things (hairstyle, face, skin tone, gear dye, face cosmetic). These do not character bound (can be traded through the bank) and will not stack with character bound ones. This means if you have 4 characters bound fragments and 6 non-characters bound fragments, you cannot make full voucher. Out of 245 chests opened, I have found 23 voucher fragments (5 cosmetic, 2 faces, 2 hairstyles, 5 gear dye, 6 skin tone)
- Gold chests can drop mini-elixirs (25% healing). These have a fairly rare chance of dropping.
- Gold chests can also drop blue and green crystals.
- Crooked Canyon: The wooden chest behind Urza will always spawn there every 10 minutes making it an easy place to have a guaranteed wooden chest spawn. This chest will drop the voucher fragments and count towards the achievement to open wooden chests.
- North Royal Road: This is a small map and has loads of wooden chest spawns. Chests seem to spawn in bulk at xx:00 and xx:05 every hour. There's a downtime from xx:30 to xx:59.
- Revoldic Dam: A large map but circular making it easy to fly in a perfect loop hunting for chests. Chests seem to spawn in bulk at xx:30 and xx:40 every hour. There's a downtime from xx:00 to xx:29.
- Here's nightmarecake's data on opening many many chests.
- Chests are not instanced, if someone loots a chest that you see, you won't be able to loot it.
- You can change channels to find more chests.
- You can use the command /nextchan and /prevchan to quickly change channels to farm chests. These are variations of the same command: /previouschannel, /lastchannel, /backchannel, /prevchan, /lastchan, /backchan, /nextchannel, /nextchan.