I think a lot of people make the mistake of building Mercury for pure healing even though she lacks the consistent healing to make those

Abilities

One level in %Backlast at start in case you get dove early. Second ability %Cinnabar for same reason.

Generally want to max %Cinnabar before anything else but if you are consistently taking fights and hitting %Magic Mortar you can level that instead. Take %Golden Beam whenever possible obviously.

Max %Magic Mortar second as your main damage ability and %Backlast last as its already such a strong dash. Feel free to take early value levels in %Backlast if you need to run from divers.

Max %Magic Mortar or %Cinnabar ?

Generally speaking, maxing %Cinnabar is best for the sustain. Even if this build does prioritize DPS somewhat 9 seconds off Q CD is absolutely insane.

Only max %Magic Mortar if you have a second healer on the team and can afford to prioritize DPS. The faster projectile is incredibly useful, but Q max is just better.

Grips

Not building @Longclaw Optics honestly feels like trolling. It gives her so much extra poke there's little reason not to as an artillery character. Second grip however you have options:

@Burning Palm (triggers whenever an enemy enters your cloud, even if they exit and step back in. Very nice for poke)
@Chrono Gauge (CDR triggers every time an enemy enters your cloud, good if you need healing for a team that's prone to taking a lot of damage like a Hudson or Kingpin)
@Feytech Claw (if you really need to sustain stupid teammates)

DON'T BUILD @Bubble Frog IT IS BAIT. You don't have enough healing in your kit to justify Frog, and all your healing outputs such insane numbers as is that putting a shield on top of it is excessive.

Kicks

@Rocket High-Tops to get away faster. Basically no other kicks really worth running. Nimbus are good if you wanna play around abyss.

Relics

Build @Isochron's Timestaff first literally always as your cooldowns are too long for @Ardent Songbow to be considered seriously. Not to mention that (even though you do a lot of poke with LMB) you aren't going to be hitting consistently enough for Songbow to be good.

Beyond that you have options for your second Relic:

@Sword of Seven Suns is your best option for poke and most other scenarios as it buffs your LMB, RMB, and ult. Your dash is so bonkers strong as Mercury and you're sitting so far in the backline that the decrease in mobility really doesn't matter.
@Ultimate Diadem level 2+ is very strong if you are consistently taking teamfights. Your ult is incredibly strong so being able to spam it more often is great. And the boost to stats certainly help.
@Paladin's Primer good if you want to lean into support. Good against slow / anti-heal spam like Felix, Kingpin, Celeste, and @Frozen Palm fans.
@Sunweaver is nice to boost poke. Consider building it in a hyper-poke loadout against bunker comps with Oath, Hudson, Shrike, etc. Take it alongside @Burning Palm basically.
@Vive Infusor good if you're getting focused a lot. Basically the "I keep getting dove by Brall :(" Relic.
@Guardian Angel good if your team is stupid.
Typical "I am long-ranged baby please don't hurt me :(" Relics of @Airblaster / @Battlegum as needed. Battlegum very nice for "build your own Oath" and firing down range from behind the funny wall can be a real pain in the ass for any diver. Airblast works but is somewhat redundant when you can just jump away instead.

Bait Relics - These technically work but I wouldn't go out of my way to build them:

@Harmonic Edge seems appealing because of how much you spam but Mercury's value is in fire-and-forget. You aren't hitting your 4th shot consistently, and even if you are just maxing out a full barrage to blast someone down is better.
@Rumel's Hoverwinger Tier 3 - The tech you can do is funny but it's massive overkill. @Vive Infusor or just a @Rabbit Paw better if for some reason you need to run away that bad.
@Duality is bait unless your team is really dumb and needs constant babysitting. You will rarely be in situations where you can activate Duality consistently: Seven Sword is better for consistency.

Perks

The only truly mandatory perk is @Farsight as it lets you see people at a distance to set up RMBs or just prepare an LMB barrage. As an artillery character a lot of your time is going to be spent "looking down a telescope" as it were. (For similar reasons @Nocturnal is okay.) Beyond that you do have plenty of options:

@Dash Engine is ait to keep your mana up.
@Grace can work as a long-ranged poker, especially since you can get yourself back to full easily by Qing yourself. Wouldn't be my first pick but it works.
@Second Skin good for a bit of defense in a pinch.
Obligatory @Amplified Haste that's literally never not useful.
@Glider Coolant / @Glider Booster are both actually quite nice to play around abyss, given your artillery nature.
@Regenerative Armor (otherwise known as "Baby's First @Autorepair") is nice as someone who is consistently in the backline. Has good synergy with @Second Skin
Typical "I have too much money and don't know what to do with it" perks (@Ever-Oracle @Oracle Immunity @Prisma Collector)

Bait Perks - Pick them up if you find them I guess don't go out of your way to buy them.

@Heal Booster is a little redundant when you aren't outputting consistent healing. Not only that but your healing is so strong as is that this becomes excessive.

General Strategy

Mercury is consistent at all points of the match. Early game you have incredible healing with %Cinnabar and late game your %Magic Mortar and %Firecracker Lance poke is very strong. At all stages of the game %Backlast can let you run away from most problems unless you're getting run down by a Joul or Felix or something (or just getting funny CC chained to death.)

You get a very big powerspike at 7 when you first level %Golden Beam so trying to either kill hatchlings for early 7 or take fights early day 2 is a smart move. Adjust your build strategy based on your team comp, grabbing early game boosts like @Feytech Claw if fighting early or playing safe and farming on late-game teams.

Generally speaking most of your time is spent spamming poke with %Firecracker Lance. %Magic Mortar should primarily be used for poke as the projectile is easy to dodge when paying attention and using it up-close makes you vulnerable, taking more damage while charging the ability. %Cinnabar is your panic ability to pop if someone gets low. Consider it akin to placing a dispenser in Team Fortress 2 or Soldier 76's healing field in Overwatch: it's meant as a quick patch-up in a safe area, and obviously you can pop it on wisps as needed.

%Backlast to run away %Golden Beam in big teamfights I shouldn't have to explain this.

Armory

Regenerative Armor

Armory

Regenerative Armor

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Builds Using Regenerative Armor

Test

Artillery Mercury

brainrot Wukong

Green Guardian

Solo to Legend Build (2)

[1.2] SPAM UNTIL NERFED

Zephenox's Joule build

Mercury! Hybrid

Dueling build

Related Equipment

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Builds Using Regenerative Armor

Test

Artillery Mercury

brainrot Wukong

Green Guardian

Solo to Legend Build (2)

[1.2] SPAM UNTIL NERFED

Zephenox's Joule build

Mercury! Hybrid

Dueling build