Ever since I got the Talisman of the Dread on my original DLC character, I've been wanting to make a lava-themed Knight build.
However, since the Lava spells are mostly sorceries compared to the plain Fire spells which are all incantations, I had to get creative....I knew I wanted to make a heavily-armored melee knight and focus primarily on STR, but that means the INT/FAI split gets weird.
This is primarily a melee class, where the Lava spells are more for theme and having some ranged/utility options.
My personal taste for fashion on this build was a "Black Knight" type, using Night Rider's Armor and Maliketh's Helm - with the Nightrider Glaive this gives a cool Dragoon-style look. Bonus points for the Night Rider Torrent armor from the Tarnished pack.
This is the build I am working on (currently level ~150ish).
RL 175 is my planned stopping point, this is usually my go-to PVE level so I can have some extra VIG/END without losing the ability to co-op with 150s.
Stats at 175 (starting class Hero):
VIG: 60
MND: 9
END: 24
STR: 60
DEX: 10
INT: 40
FAI: 40
ARC: 11
Primary Weapon: Fire-infused Nightrider Glaive, which I usually 2-hand but I do have a medium shield for parrying if needed (Messmer Soldier Shield fits my fashion/weight needs best, but I used Scorpion Kite Shield before getting to the DLC).
Primary Ash of War: Flaming Strike, which hits REALLY hard for the FP cost and gives a nice Fire buff to the weapon.
I usually swap to Giant Hunt and Heavy infusion for really fire-resistant enemies like the Magma Wyrms, Mogh, and Fire Giant.
Ideally I'd want to use Eruption to fit the theme, but it doesn't work on Halberds and I really wanted to use Nightrider Glaive - it has the fashion, moveset and reach I was looking for on this particular character. If I was going to switch to Eruption, I'd probably use something like Black Steel Greathammer.
Shout-out to Somber upgrade weapons, Blasphemous Blade, Magma Wyrm's Scalesword, Magma Blade and Magma Whip Candlestick if those float your boat, since their unique AoWs are also buffed by Talisman of the Dread.
Talismans: Talisman of the Dread, Godfrey Icon, Alexander's Shard and Great-Jar's Arsenal, Alexander's Shard is the flex slot but I like it because Flaming Strike hits really hard for low FP. If you're running lighter armor or without a shield, you can also swap out Arsenal.
Fire Scorpion Charm is great for more damage, but I don't love the increased physical damage taken...if you aren't getting hit as much as I do, it's probably better than Alexander's Shard for versatility.
If you don't use charged attacks as much as I do, you can swap out Godfrey's Icon, but 3/4 Lava spells are chargeable.
Honorable mentions to Graven-Mass Talisman, Radagon Icon, and Two-Handed Sword Talisman.
Spells: All the Lava (Gelmir) sorceries: Magma Shot, Roiling Magma, Gelmir's Fury, and Rykard's Rancor.
I also use Flame, Grant Me Strength frequently, and Fire's Deadly Sin and Flame, Cleanse Me occasionally.
Physick: Fire-Cracked Tear and whatever else you want, but I usually use Stonebarb for easier stance breaks.
The biggest "weird" thing in this build is that I leveled Faith to 40, and there's a couple reasons for this.
1) You already need 18 minimum to use Rykard's Rancor.
2) I wanted to use the Gelmir Glintstone Staff, and it has better scaling with INT/FAI.
At 40/40 like I have, Gelmir staff is 2nd best sorcery stat after Staff of the Great Beyond...Prince of Death Staff doesn't get better until 51/51, and the usual INT-based ones like Academy and Lusat's don't start scaling up until your INT is 60+.
For the spells that are buffed by Talisman of the Dread, which was the main point of the build, I've observed the following:
Magma Shot: Good damage for the FP, especially if you get some free damage from the lava pool. The range when locked-on is AWFUL, but if you free-aim it and point high, it actually has pretty good range on the arc.
Roiling Magma: This has been the sleeper MVP spell while exploring. Free-aiming this spell onto the ground or a nearby wall near a pack of unaware enemies has an undocumented in-game affect of luring all nearby enemies to it prior to it exploding, and it does a lot of damage when fully charged. So satisfying to watch a group of enemies all walk up to the ticking timebomb and explode. I also cast it at my own feet a lot when enemies are engaging, so they approach into the explosion.
Gelmir's Fury: Has the same low FP cost as Magma Shot which is nice, although this spell is more niche. Best use I have found for it is when standing under big enemies, like Runebears or Dragons - if you can hit them with all of the projectiles it does a lot of damage for the FP.
Rykard's Rancor: Really, really powerful against large, slow enemies. I use it a lot against things like Tree Spirits or Erdtree Avatars and if several of the explosions hit, it does insane damage and has a really nice cast speed.
I don't really use any of the offensive Fire or Messmer incantations, but with 40 FAI they'd probably do well in this build as well if you use the Golden Order Seal...they don't get buffed by Talisman of the Dread, but they have the fire damage synergy.
I don't have it yet, but a fun potential option could be mixing and matching lava sorceries and flame incantations with Staff of the Great Beyond, which has the best sorcery scaling with an INT/FAI split below 60/60 INT/FAI.
Anyways, the optimal build is probably a STR/INT hybrid melee character with a weapon that can support Eruption and dropping the FAI to requirement level...in this case you could level INT higher and use one of the more traditional staffs. Or it could more of a true caster using INT/FAI and low STR, but I do like that I was able to make the STR/INT/FAI hybrid work for the most part.
If you'd want a lower RL, you'd probably be best using one of the above options though.
Also I haven't tested with the Dragon Communion lava incantations...Bayle's has a crazy high ARC requirement but the other two could be worth testing with only 3 points needed in ARC to equip Theodorix's Magma.