Throughout the questline, the player will be introduced to various powerful equipment. The mace, shield, and staff are particularly powerful and can be upgraded during the questline.
The three main pieces of the equipment are required to complete all of the quest content and so will be flagged as quest items until the player has completed the quests.
This mace is rewarded during the Path of the Thief portion of the main quest.

Activating the Power Attack causes the player to blink forward until they reach an enemy, some sort of physical obstruction, or the max range (which is around 3000 units), at which point an impact explosion hits, dealing damage to anyone extremely close to where the player reached.
The further the player travels during this blink, the more damage the explosion will do.
This ability accounts for detection, and will do extra damage if done from stealth.
Using a Backwards Power Attack launches a projectile forward that will rag doll many enemy types it hits and pull them to the player.
This projectile is able to be used in puzzle scenarios found throughout Sigil of the Fallen to trigger the green glowing items - such as the gongs. This feature was added to ensure players who suffer from motion sickness could still complete the Thief dungeon.
If the player has Oblivion's Wall equipped in their other hand, the impact will also apply a force impact, potentially hurling the impacted enemies.
If the player has the Scepter of the Infinite Chorus equipped in their other hand, any summoned motes will also propel forward with the player, adding their potential explosions to the attack.
After completing the Thief Spirit's core memory sequence, he will upgrade the mace, increasing the damage dealt by long range blinks.
After completing the side quest Stolen Lament, he will increase this damage multiplier even further.
This shield is rewarded during the Path of the Warrior portion of the main quest.

Activating the base game Shield Slam (ie. pressing attack key while holding block) will trigger an additional ability from this shield, staggering any enemies in a small arc in front of the player.
After completing the Warrior Spirit's core memory sequence, he will upgrade the shield, allowing the slam to apply a knockdown force in addition to the stagger.
After completing the side quest Unyielding Resolve, he will extend the range in front of the player that the shield slam can affect enemies.
Synergy - Scepter of the Infinite Chorus
Holding block with Obvlion's Wall while the Scepter of Infinite Chorus is in the other hand will cause the Scepter's mote summoning ability to trigger as if the player was holding charge on the Scepter.
This staff is rewarded during the Path of the Mage portion of the main quest.
Using this item slowly contributes to increasing Conjuration skill.

Holding the attack button begins summoning small wisp-like Orbs of energy up to a maximum of 3; a sound will play each time a new one is spawned. Continuing to hold the attack key will cause any spawned Orbs to follow the player.
These Orbs will explode when they near an enemy or special activators found in a few of the quest locations (indicated by glowing blue cracks on the surface of the object).
The damage of these orbs is improved by increasing Conjuration skill.
Releasing the attack button will fire out a projectile - wherever this impacts, the Orbs will launch themselves in a straight line towards. They will continue to launch themselves every few seconds until they are within a tight range of the impact point, or the player holds the attack button again to call them to follow once more.
Sheathing the staff will dismiss any Orbs that are currently spawned.
After completing the Mage Spirit's core memory sequence, she will upgrade the staff, allowing the player to summon 3 additional Orbs, and slightly increasing the explosion damage they do.
After completing the side quest Connective Tissue she will further upgrade the staff, allowing the player to summon a total of 8 Orbs, and increasing their explosion damage further.
This item is rewarded during the unmarked The Flask side quest.

The Flask can be activated to spend 5 Ectoplasm in exchange for fully restoring the player's Health, Magicka, and Stamina. The player will be prompted when using it to confirm expending the Ectoplasm. If the player activates it without enough Ectoplasm in their inventory, a message will warn them as such.
Using the Flask does not expend it, and a replacement will be given to the player instantaneously.
This ring is rewarded as part of the unlabeled side quest referred to as The Name on this wiki.
The ring uses the Silver Ring model and provides the muffle enchantment, allowing the player to move silently.