use [Phenmor] or [Tenet Arca Plasmor]

How to Survive
Part 1: Don't get hit!

Mag has lots of tools as her disposal to allow you to keep yourself, or even your allies, in peak condition.

First and foremost, she has her bubbles to use as shields. You want to keep all three of your Magnetize bubbles active at all times, then position yourself between them and the areas enemies are attacking you from. These bubbles will prevent any enemy gunfire from reaching you, as it will instead be absorbed by the bubbles. Along with this the bubbles will also suck in any enemies that get near and deal damage to them each half second. A strong offense and effective defense all wrapped up in one nifty little ability.

Along with her bubbles, you are able to use her plentiful access to strong crowd control. Mag's first ability, Pull, as well as her fourth ability, Crush, will keep the feet of your enemies off the ground, thus preventing them from attacking you.

Part 2: Shields and Shieldgating (Decaying Dragon Key!)

Those are the ways to keep the enemies from attacking you, but they will occasionally be able to hit you by getting past your bubbles, the first line of defense. When this happens she has other tools to keep herself alive.

Whenever your shields are depleted, you will be granted a period of invincibility, called the "Shieldgate". The duration of your Shieldgate depends on if your shields were fully recharged since last depletion.

If your shields reached 100% since last depletion, then you are granted a full 1.3 seconds of "Shieldgate".
If your shields were only partially charged, then you instead get 0.33 seconds of Shieldgate.

So as you can imagine, this Shieldgate would be a very good mechanic to exploit for staying alive in a pinch, except you want the full 1.3s as opposed to the 0.33s.

You always want your shields to be at 100% between shield-breaks for the full 1.3s Shieldgate duration, meaning you also want abilities that replenish shields to give 100% of your shields in one cast. If you have less shields you're able to replenish them with less ability strength, and less total ability casts. Following this logic, you want to minimize your total shield capacity so that every cast of Polarize and Crush, even with low ability strength, will always give the full 1.3s Shieldgate.

This brings me to my next point, the Decaying Dragon Key. This gear item reduces your total shields by 75% for simply having it equipped, meaning it lowers your 450 unmodded shield value down to 113. Having 450 shields you need to actually build for ability strength to fully replenish shields in one Polarize cast, or you can cast multiple times with low ability strength. However if you reduce the total shields you have to only 113 then you can replenish them in a single cast, even with only 80% ability strength.

Since Shieldgate duration is based off of your total shields excluding overshields, this means you can still replenish your full overshields with Crush, and end up at 1300 shields. You can do this while keeping your Shieldgate low enough to refresh with a single cast of Polarize.

Part 3: Modding

If you are having trouble staying alive despite all of this, jump back up to the modding section and take a look at the survivability choices shown.

Section Summary: Use your bubbles and crowd control to keep enemies from hitting you, when you get hit use your shield replenishing abilities (Polarize or Crush) to reset your Shieldgate. Can substitute some for Rolling Guard or similar survivability mods if needed, but that's really all there is to it.

How To Play / Playstyle
There are two main distinctions to make, enemy type, and playstyle.

Your enemy type depends on if enemies have armour, so they are either Armoured or Unarmoured.
Your playstyle depends on your preference, whatever you find more fun. The playstyles as I like to call them are Active or Lazy.

If you are against armoured units you will want a slash capable projectile weapon, like Exergis or Tenet Arca Plasmor. These weapons are ideal as the projectiles themselves are capable of directly hitting enemies dozens of times thanks to the way the bubble works. You will place bubbles and wait for enemies to cluster up in them, then feel free to unload and Shred them with your slash based weaponry!

Armoured Demonstration: youtube id="https://www.youtube.com/watch?v=gbrHUmYCpys"

If you are against unarmoured units you will want to prioritize pumping raw DPS into your Magnetize bubbles. This means after you place down a bubble you will want to unload a magazine or so from something like your Akbronco Prime. This will add hundreds of thousands of damage to your bubble's damage over time effect, meaning it will instantly kill anything without armour that touches it.

Unarmoured Demonstration: youtube id="https://www.youtube.com/watch?v=Hu81eatWei0"

Active Play

Active play revolves around finding a room or area that you and your squad are happy to chill, and vibing there. When you are in a room you want to be mindful of the areas enemies mainly Flow in from, so I normally pinpoint the three most used doors and place bubbles down in these. You will just keep your bubbles active in the main choke points for enemies, and then kill them appropriately depending on if they have armour or not. You will basically just be juggling bubbles in the main chokepoints while you jump around and kill things, it's quite pleasant.

Lazy Play

This style of play revolves primarily around corner camping. You want to find a good spot with a dead end, like a hallway, and then park yourself in the back of it. Once there, you will place a single bubble in the only hallway leading to you, the only area enemies can funnel through. Once you've got your bubble set up, blast away! It's really this simple. Just remember, always keep a bubble active, that's what keeps you alive and keeps you dealing damage.

So basically, here are the few key things to focus on while playing [Mag].

Always have your maximum of 3 Magnetize bubbles active at any given time.

Position yourself with the bubbles between you and the enemies, to use them as cover.

Cast your 3 when your shields are broken, to reset your shield-gate. Can also use 4 which CC's enemies as well as shield-gate resets, but has higher energy cost.

Cast 4 to crowd control and knock down a room, allowing free time to res allies or just for a second to breathe.

Cast 4 to grant allies overshields, topping them up, granting them a bit more EHP.

Closing Notes:
This is a general use build. There are not many situations where I would suggest other builds, but if you are planning to bring Mag into something like Elite Sanctuary Onslaught then you can find a build below suited to that type of mission below.
https://overframe.gg/build/221612/mag/mag-goddess-eso-nuking/ - ESO Nuker Mag

I appreciate you all reading this and sincerely hope it's helped. I love playing Mag and wanted to spread the joy!

As an aside, I am very into game design and have spent countless hours writing Warframe Rebalance concepts. Long story short, I wrote an in depth Mag Mini-rework/Rebalance! It's over on the Warframe forums which I will provide a link to below this. If you want to support me in my journey to improve Warframe, or even just Mag herself, then feel free to head on over and like it or drop feedback in the comments!

https://forums.warframe.com/topic/1314272-warframe-rebalance-mag-mini-overhaul/ - Mag Mini-rework

Your time is absolutely appreciated Tenno, I just hope I was able to give you something in return for it!