Destiny: Rise of Iron's new social space - the Iron Temple - has a number of secrets hidden up its sleeve, but the most interesting surrounds giant bells.
There are six bells inside the temple that, when played in the right order, unlock one of the expansion's Trophies / Achievements, Sing the Iron Song. Here's how to do it.
Bell order locations in Destiny: Rise of Iron to unlock Sing the Iron Song
In the Iron Temple, go up the steps into the main temple entrance. From here there is a circular level above where the six bells are located; one up above where you enter, and the other five round the back.
Using this as a guide, the order of the bells are as follows - 1 is the one above you, and from left to right from here facing the rest of the bells, go from 2, 3, 4, 5 and 6.
Bell order to unlock the 'Sing the Iron Song' hidden Achievement / Trophy in Destiny: Rise of Iron
Now we have the order of the bells down, they need to be rung in the following order:
1, 2, 3, 1, 5 - 4, 3, 2, 3, 1
You'll notice you don't use the sixth bell - don't worry about that, it's either a red herring or is used for something else entirely.
Since you need to ring each bell in quick succession, there is no way to do it solo. Ideally you'd have a player placed at each bell, with someone calling out the order (you can start ringing the bell as soon as you hear the last one, since it'll take a few moments for the interaction to follow through), but it's possible to have just one person do the entire row of bells if they're quick enough. Practice makes perfect!
This video from Maka91Productions shows the location of every bell and their order very clearly:
If performed correctly, you will hear a unique whooshing around and the the Trophy / Achievement will unlock. Why this order? This is the tune of the expansion's main theme, that you can hear here:
Want more Destiny: Rise of Iron guides, tips and tricks? Then read our Wrath of the Machine walkthrough and guides, complete list of all Dormant SIVA Cluster locations, tips on how to reach Destiny's max Light level, how to complete the Exotic Gjallarhorn Quest, Khvostov 7G-OX Quest and Thorn Quest and new modes Vanguard Elite Strike Scoring and SRL.
What else does ringing the bells in Rise of Iron do beyond unlocking Sing the Iron Song?
Right now, not a lot; it's speculated that could be more hidden secrets if you ring the bells in the correct order, and we'll hopefully know more in time.
Until then, with the notes provided, you could probably other songs if you and your Fireteam co-ordinated yourselves - so expect plenty of YouTube videos of that in the weeks to come...