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.
Almost all Banners affect just your team, unlike most other Relics. They can restore Life, Stamina or boost the stats of your team.

Darmith's Banner: This is the first Relic to feature any form of Damage Protection, Darmith's Banner gives all allies Armor and Fire Protection in addition to increasing their Base Strength. This makes it an excellent offensive - defensive hybrid relic that can not only protect, but also increase damage output.

Talika's Banner: Talika's Banner resembles other relics like Tenacity Shield and Talany's Mask, and it has its ups and downs compared to them: its boost stays forever, but in exchange for this, your monsters aren't protected from Torture effects. Still, this is a useful Banner to protect your team from attackers.

Ingvar's Banner: This Relic is great in fights that will drag on to gain massive momentum from both the Life and Stamina restoration, or just to reduce the damage of Torture effects and attackers. It's also a great weapon against Stamina Drain after some point.

Charging Banner: This is better than Ingvar's Banner at combatting Stamina Drains, and absolutely devastating if an extra turn spammer can hold it, like Zyla.

Vitality Banner: Inferior Talika's Banner.

Furious Banner: Too unpredictable, skip.

Haste Banner: Same situation as Furious Banner, skip.

Life Banner: Inferior Vitality Banner, but way less powerful.

Enraged Banner: Inferior Furious Banner.

Swiftness Banner: Inferior Haste Banner.

Revitalizing Banner: Inferior Life Banner.

Drummer's Banner: Skip.

Energy Banner: Too unpredictable, skip.