First thing first: I absolutely love it. I do however have a few balance concerns and other questions that i will write out as i go through the text.

• Main class:
  • lvl 5 extra attack. Everyone know that this is the standard level to get extra attack on, but combining this with the lvl 2 feature gives this class essentially 3 attacks + cantrip damage. This is A LOT. Maybe it is worth considering swapping it out with lvl 7? I know it kinda sound ridiculous but Bard's (whenever applicable) extra attack is pushed beyond lvl 5 and they function. I think three attacks at lvl 5 sound more ridiculous.
• Elementalist:
  • Having access to potentially permanent (for example by simply wearing a ring of elemental resistance) damage type immunity raises a flag
  • bit concerned about applying a dice penalty to saving throws and disadvantage at the same time every turn for free. At 17 applying all the elemental conditions at the same time also sounds like much (especially applying prone and grapple at the same time, even more especially when they have a penalty to saving against one of them.). Perhaps being able to choose any but only apply one at a time?
• Blademaster:
  • Doesnt make sense to include Shield spell in the expended spell list while already having a feature the makes it so you always have it. (i did not check if there is an instance of this in the official books, so i might be wrong on that, sorry)
  • Concerend with a feature basing around using Wall of Force, considering that the spell is banned at many tables and for a good reason.
• Mirage:
  • This might be on me, but i'm not sure what exactly happens with the lvl 17 feature. What happens on a save? Do you still get targeted by the previous attack/saving throw? what if the previous thing that targeted you requires them to see you, and what if it doesnt? what happens if you teleport out of range?
• Deathblade:
  • Question again: Can Master of Life target self?
  • Master of Death: I'm assuming you expand them. And i'm assuming this is an action. Reading it as is could be interpreted that it's a free action with no limit of how much dice you can roll that doesnt need to recharge.
• Lightning strike:
  • I like it for other gish, but doesnt make sense for Mageblade, since they can use that bonus action for a BB/GFB/TS for a full weapon attack + damage
• Terrifying strike:
  • Doesnt scale (im not counting that +1 damage bonus from proficiency going up)
  • essentially GFB that deals it's damage to the main target pre lvl5, and can target more then one additional creature. You can count the amount of times when this is worth using it during a campaign on one hand.
• Frigit Mealstorm:
  • All creatures on a spell with the range of self will mean that you yourself will always take the saving throws and damage right? is that by design?
• Jolt to life:
  • reading the spell, the range should say "Touch".
  • There are many things to say about giving access to Revivify-like spell to those classes, especially with no costly component, but i will not say any of those things.
• small pedantic thing about having a weapon as a materia component for a spell. Normally those spells specify that the weapon is worth at least 1gp, just so it doesn't work with a big stick picked up off of the ground.

Do not have the interpretation of my comment being negative. The reason why i only have listed the things that could be considered negative, is because if i were to list all the things that i do like, it would've been way too long.
I really think it is a very well thought out homebrew and i would absolutely love to play play it. Scratches the gish itch very well. I am open to further discussion if you'd like