Once a part of an angelic being known as Iutia, Reason was splintered off in Iutia’s dying breath, along with Spirit and Desire, each with a sole purpose - guarding their respective key fragments. This is the only objective that actually matters to the construct; its own disrepair matters not so long as the fragment is safe.
Reason's fight has two main "phases" - each activating with the gain or loss of Hardy Build.
While it has the effects of the temporary health from Hardy Build, Reason is slow, lumbering, and like a walking tank. With the mixture of Measured Stance and Reflective Shell, Reason is not only is immune to all Conditions, but it also gives your ranged archer and spellcasters a hard time by sending their missiles right back at them. Its move speed is reduced, and is way more defensive than offensive.
When it loses this temporary health though, Reason becomes a force to be reckoned with. It gains more attacks, and each attack does more damage through Marks. Each time a target is struck by Suon while Reason is in its Erratic Stance, they gain a Mark. Marks continually accumulate throughout the fight, but only have an effect on Reason's turn. At the start of Reason's turn, the target takes 1d4 Radiant Damage per mark. So...long story short, if your players mess around on this fight, they're gonna have a bad time.
Reason doesn't have much of a personality. It was created with a purpose, and fulfills that purpose. Now, that doesn't mean it has no personality at all, but it's personality could be based entirely on someone who passed through. What kind of personality do you think Reason should have?
Once a part of an angelic being known as Iutia, Reason was split off along with two similar constructs, Spirit and Desire. A key was split into thirds, and each construct entrusted with protecting a fragment of it. It's said that not even the constructs know what this key is hiding. How much treasure could be hidden. Whatever is being protected, it must be worth it.
Reason is generally a slow, lumbering behemoth. Reason is quiet, and measured, until enraged. A lightly ominous track that still feels well structured is good for any roleplay that could happen. Siege Dancers from Destiny does a good job with this!
Once combat hits, we still want to hit that same feeling, just with some more weight and intensity to it. Kell's Fury from Destiny 2 hits that mark very well. If you want to hammer home the feeling even more, you can switch to Phase 1 of Kell's Fury while Reason has Hardy Build, and Phase 2 of Kell's Fury when Hardy Build is gone.
