Hello everyone. I felt the need to do this since unlike Runes, Relics get new additions once in a while, and it'd be a chore to update every single one of my analyses just to add said Relic to my list of options. Instead, I will analyse every respective Relic here and tell in which situations or on which kind of monster they'd be useful on so that you may experiment more freely and I may relieve myself of the need for updating my past analyses.
Before beginning, I must mention that some Relics are obviously weaker than others and some Relics are not useful at all. To more effectively show this, I will list the higher powered Relics before those inferior ones so that you can know the one below is weaker than the one above, but can sometimes be used as a substitute if you don't have access to the latter.
Like Shields, Armors focus on survival, but almost all of them have effects that benefit just the wearer in exchange for greater protection than Shields in general.

Atum's Armor: This Armor gives good protection with no conditions, making it one of the best Armors overall. It can be used to help alleviate frailness issues on some monsters, or simply to prevent an enemy attacker from one-shotting a key monster on your team.

Nebotus' Armor: This Armor is something like a reset button, and is one of the best ways to combat Stamina Drain. If you're up against monsters like Storm Beard or Wangzhou this is among your best answers to them. It also handles Torture effects really well thanks to its ability to proc 2 times during a battle.

Thetys' Armor: Solely focusing on Stamina Drains, Thetys' Armor can be perfect against Stamina Drain monsters like the aforementioned Wangzhou, since being below 25% Stamina will trigger the Armor, causing the enemies to also lose all their Stamina. If not against those, it can still deny an attacker that tries to attack the wearer thanks to its above 75% Life effect.

Heavy Duty Armor: This is a somewhat inferior Nebotus' Armor, but it can proc above 50% too, which can make it more useful in some cases.

Armor of Duty: Most of the time, this is an inferior Heavy Duty Armor.

Cold Armor, Earth-Shaking Armor and Soul Armor: Inferior Armors of Duty.

Spirits Armor: Inferior Soul Armor.

Oniric Armor: Very situational with not too great of an impact, but it's a Bronze Relic so that's to be expected.

Widow Armor: You want your monsters to be alive, not dead. Skip.

Charging Armor: This is a heavily downpowered Nebotus' Armor, but it's the most useful Bronze Relic since it can allow you to fight 100% Stamina Drain.

Despair Armor: Very inferior Heavy Duty Armor.