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.
Amulets have a wide variety of supportive effects, like Stamina control, survival and stat boosts. It has a Diamond Relic that's among the strongest ones in the game too.

Sherezar's Amulet: And that Relic is this one. Sherezar's Amulet is excellent on any monster, since after a level it will drain more than 140 Stamina, which is the normal maximum Stamina Legendary monsters have, making it a built-in deny move. What's more, it can proc more than once, so you can deny enemies twice if you have 2 AOE attacks. Deniers escpecially enjoy this since their deny effect will happen alongside the Stamina Drain, making the enemies denied for 2 turns.

Alces' Amulet: Alces' Amulet is best used by tanks that have Amulet slots. Other than that, it could be used to keep a centerpiece monster alive.

Frostbite's Amulet: This is an inferior Sherezar's Amulet. You can use it on an attacker with AOE Freeze, but just dealing damage could be a waste in this slot.

Osur's Amulet: This is an offensive Amulet that can be useful to power up an attacker, or to outspeed a certain monster your enemy has at a certain time. The buffs it gives are very helpful for attackers to outspeed an enemy attacker, since it's usually kill or be killed in a single hit between attackers , making Speed crucial.

Kinetik Amulet: An inferior Osur's Amulet that gives the boost to a single random ally, which makes it risky and usually not worth using.

Supercharged Amulet: This Amulet is especially useful on monsters that have Stamina costs above 140 to not waste a slot on a Stamina Rune, or extra turn spammers to make them infinitely stronger. Other than those, it may be a bit underwhelming since Stamina Drains happen based on percentages and 100% Stamina Drain will always drop you to 0 because of this.

Grieve Amulet: You want your monsters to be alive, not dead. Skip.

Widow Amulet: Skip for the same reason.

Amulet of Haste: Underwhelming, skip.

Minor Grieve Amulet: Skip.

Protection Amulet: Craft other, more impactful Amulets. At least more usable than the skipped ones.

Healing Amulet: Very inferior Alces' Amulet.

Amulet of Swiftness: Inferior Amulet of Haste.

Energizing Amulet: This can actually be useful to combat 100% Stamina Drain. You should put it on a monster who can utilize the little Stamina it gained so that it can be impactful. It can be used 2 times as well, so you'll get 2 moves off over 2 turns.