Hi

How can I build a heavy armour wearing, spell caster, who can also use a shield and sword, but whom is not a Paladin or a multiclass.

I really want to make a chaos powered Battle Mage, who draws his power from the abyss, like a demon but who is not a demon 

Someone who wears heavy plate armour, and specialises in using magic to control the battlefield.  But who can just as easily weild a sword and shield against his foes

I mean like at high levels, I am imagining him using magic to literally bend minds and warp the battlefield, creating utter chaos that fractures reality itself.

Okay, so I know that no mortal magic user can ever be that powerful, but that is the concept that I have in mind.

How can I get at least close to that kind of character..

 With a mountain dwarf you get medium armor and Dwarven Combat Training
You have proficiency with the battleaxe, handaxe, light hammer, and warhammer.

With an elf you get proficiency with the long sword. 

In both cases you would need to take a feat to get heavy armor proficiency. 

So as a variant human you could grab that feat and wield a sword.  The only thing you won't be able to do is add your proficiency bonus using the sword. 

What's wrong with clerics, eldritch knights and hexblades?

War domain cleric gets heavy armor and martial weapons

Otherwise you need to spend one or more ASI's. The options that only need 1 ASI are Dwarf, Valor Bard, Swords Bard, and Hexblade Warlock.

3 levels of fighter, the rest of wizard?

Will eventually give you access to 9th level spells and gives you heavy armour from the word go. Pick eldritch knight for extra cantrips and spells.

Quote from Paladin54 >>

 

So as a variant human you could grab that feat and wield a sword.  The only thing you won't be able to do is add your proficiency bonus using the sword. 

Just remember there's a prerequisite.

Heavily Armored: Prerequisite: Proficiency with medium armor

Quote from Account_of_Holding >>

Quote from Paladin54 >>

 

So as a variant human you could grab that feat and wield a sword.  The only thing you won't be able to do is add your proficiency bonus using the sword. 

Just remember there's a prerequisite.

Heavily Armored: Prerequisite: Proficiency with medium armor

 Oh yeah,  So mountain dwarf would work well as a spellcaster to get the flavor the OP is looking for.

Hexblade / Sorcerer Warforged. High dex with the medium integrated protection / shield and cloak of protection can get you to AC 20 at level 4. Take shield as one of your spells and you’re at AC 25 in those critical moments. And Warforged AC scales based on prof bonus. Currently playing one now in our office game and loving it.

Yes.   I love the warforged.  Not needing to breathe is super handy when dealing with water too.   

SocialFoxes, you want to play an Arcana Cleric. Trust me.

I would suggest a Tempest Cleric. You get heavy armor and martial weapons, blast enemies for hitting you, a ton of great spells to damage or control the battlefield, and the option to heal on top. Just work with your dm to reflavor/skin some spells to suit your theme and work out a diety/patron to derive your powers/blessings from.

Okay, I think I've got you covered. It'll be weird but... Play a wizard. Now here's the trick, wizards get 5 ASIs so you'll want feats instead. (this mean you'll need good ability scores from the start but...)

For your armor needs take Lightly Armored, Moderately Armored, Heavily Armored, and bomb heavy armor and 2 ASIs left.

You'll need a race that gives weapon proficiency or you don't like the race options then also take Weapon Master and then you have four weapons of your choice at the cost of 1 ASI.You may want to use 1 ASI for weapon flavor... Sharpshooter, Duel Wielder, or Great Weapon Master for one ASI per.

You will still have a low health pool. Tough can help a little with that but not much.

And I don't think you can get shield use without MCing.

I think I've got close to your mark (as long as you don't mind the lvl progression). And if I haven't someone will correct me.

Quote from Cynroc >>

For your armor needs take Lightly Armored, Moderately Armored, Heavily Armored, and bomb heavy armor and 2 ASIs left.

 

And I don't think you can get shield use without MCing.

That's a ridiculous amount of feats. You would get shield proficiency from Moderately Armored, but a single level dip into Fighter gives you all of those proficiencies & more.

Arcana Cleric. 😉

Only if you start fighter.   If you dip fighter after you don't get heavy armor.  But it would reduce the feats needed to just the heavy armor feat. 

Quote from Kaynadin >>

Only if you start fighter.   If you dip fighter after you don't get heavy armor.  But it would reduce the feats needed to just the heavy armor feat. 

You are right, I misread. You could also do the same thing by just being a Mountain Dwarf.

Without multiclassing?

Arcana Cleric. The wonderful thing about dnd is the ability to retheme and reflavor to your desires, provided your DM is okay with it. You can grab cantrips like Booming Blade and Green-Flame Blade to really go towards the spell blade.

Pick up variant human, nab magic initiate druid for Shillelagh, and you're suddenly very S.A.D., needing only Wis and a min of 15 in strength to get your heavy armor. You'll still have to grab the feat at level 4, but this way you're not punished by nabbing a feat instead of bumping an attribute. 

Then just retheme your spells and features to the Abyss instead of a god. Mechanically, all the same. Thematically? You're an abyssal channeler in full plate cracking heads and casting spells.

Oops, I missed the "no multiclass".

Battle Smith Artificer has kind of a palladin feel to it without all the trappings of chivalry and oaths and all that. I'm pretty sure they can have heavy armor and they might also get smite spells, along with all the great utility spells from the class.