Wanted to try something, it became this thing. I guess you can make it a Boot Camp of sorts. Heh.

Veritas of the Flame Physical Finisher

7★ abilities:

His Trust Ability does a lot of things, a good chunk of it helps him immensely. He doubles the % needed for his innate counters to trigger, from 20% to 40% when hit by magic attacks to trigger Fiery Retribution (ST 3 Turn -100% Fire Resist), and from 40% to 80% when hit by physical/magic attacks to trigger enhanced Uplift 2. Also, it gives him axe mastery.

With recent trials having both physical and magic AoE attacks, the value of his counters on him go up. Even in 7★, his best finisher is Full Charge Stomp via Uplift counter, it's a 1240% mod finisher that's locked behind a counter. It was awful since he initially had 40% chance to proc it, now, it's somewhat reliable.

Big Swing realistically does nothing for him considering that Heavy Stomp 2 has the same modifiers and is part of his finisher rotation without relying on Uplift. His non-counter finisher rotation is 2x "Axe" -> Heavy Stomp -> Power Stomp (unlocked via Heavy Stomp 2) -> Heavy Stomp -> Power Stomp. With his 'axe' abilities inflicting imperil AND imbuing himself for 5 turns, the following Stomp abilities will benefit from the imbue and imperil. Power Stomp has a 1000% mod, so it's not a major loss in damage compared to Full Charge Stomp.

His first CD ability, Anger Blaze, is a massive self ATK buff and counter buff. I don't recommend using this due to how stacking counters passives work.

From the wiki:

The Counter skills can stack if coming from different sources, though that only increases the likelihood of a counter, not the quantity.

You may counter up to a single time per single attack your character sustains.

It also reduces the odds of a specific counter occurring, since each hit is checked through each counter ability, if it procs the first counter then the following counters aren't checked. Between Fiery Retribution and Uplift, only Uplift can trigger from physical damage, and since Anger Blaze counter only procs on physical damage, there's a chance that Anger Blaze counter procs instead of Uplift.

His 2nd CD ability, is devastating. 3000% Fire finisher is nothing to scoff at. It's just as a ridiculous as Dragonlord's Kafrizzle 2 (though Kafrizzle has better mods if Dragonlord is a 7★, they have the same mods otherwise, just different damage types). Sure, it'll be available on Turn 4, but VoF and the ST enemy are still under the effects of his Axe abilities if you followed his rotation, meaning a 3000% Fire modifier attack can also proc on a -50% Fire imperil (assuming you used Flaming Axe and it's -100% imperil if you somehow proc Fiery Retribution). That's a lotta damage.

His new rotation for 7★ is 2x Flaming Axe -> Heavy Stomp -> Power Stomp -> Red Inferno -> (repeat). It's locked to Fire, I don't recommend running this rotation of Fire resistant enemies.

Lastly, Forging Arm grants him 10% Physical Mitigation permanently (as a buff, it won't stack with Pod 153 or Barusa's physical mitigation buffs) and more axe mastery and a DEF version axe mastery. If you factor his previous passives into the mix, along with his TMR, a level 120 Veritas of the Flame with an axe, heavy armor, and his TMR on him, he has 280% ATK. The man is barely hitting the 300% stat cap with minimal gearing.

However, he isn't like Dragonlord where he's ready to burn every single thing in sight at the get-go, he needs to setup and wait until Red Inferno is ready. His slow start makes him unreliable for First Turn Kills, but his damage is strong enough to where he's a reliable solo DPS unit like Emperor and Dragonlord.

Trials are where he can shine the most, if a 3★ base Shantotto can solo DPS the Bomb Family trial, then I'm pretty sure you can slot 7★ Veritas of the Flame as a solo DPS just fine. Citra's Extra Stages is probably the best place to give him a spin right now if you have the resources saved up just for him.

In case you're curious on how ridiculous 280% ATK can be, here's a TDH Fire Veritas build. Credit to /u/DefiantHermit for the build.

In short, Fire Veritas is a nutty finisher with a slow start but godly damage output.