SOURCE: Xanathar’s Guide to Everything

Rating the Benefits of Infernal Constitution

Benefit #1 – 

+1 to Con, to a max of 20 

Half an ASI is a benefit many feats offer, especially as 5e evolves. This means the rest of the benefits here are only really worth half a feat. 

In terms of stats, Con is decent. Every character always wants more Constitution, and considering the rest of the feat is about fighting through damage and passing Con saves, a higher bonus is welcome. 

Benefit #2 – 

Resistance against Cold and Poison damage

Twin damage resistances are good, especially on the Tiefling, which is naturally also resistant to Fire. 

Both Cold and Poison are widely dealt damage types, and being able to flatly halve damage received is a major defensive benefit, especially if you’re in a campaign where these are commonly faced. 

Benefit #3- 

Advantage on saving throws against being poisoned

Poisoned is a strong debuff if it lands, conferring disadvantage on attack rolls and ability checks, including skills. 

The problem here is, that many enemy types and encounters won’t feature poison, at all. If this comes up, it’s very useful, but in many campaigns expect this to rarely feature. 

Mechanics and Requirements

Understanding How It Functions

Infernal Constitution does three things, all of which are based around a single tight focus: Getting tougher. 

An Ability Score Increase In Con

Many feats offer an ASI. Infernal Constitution is one of them. 

Unsurprisingly, considering the name, the boost is in Constitution. And only Constitution. 

That’s a shame. Many feats offer an ASI in at least a choice of two stats, offering a little more flexibility when choosing a feat. 

Still, out of all six stats, Con is far from a bad option to have as a locked boost. Every single character in 5e always needs more Con. It dictates total HP, Concentration checks for holding onto spells, plus the all-important Con saves, which can keep a character safe from a whole host of horrible conditions. (No foreshadowing at all here…) 

It’s just a shame that there’s no variable, or second choice here. We feel like with that, it would have made it much simpler to fit the feat into a wider variety of builds.

Resistance against Poison and Cold damage

Damage resistance is one of the simplest ways to massively increase a character’s toughness in D&D 5e. 

When a character or other creature has resistance against a source of damage, they cut the damage taken in half. No checks, no having to make a roll. Just half damage. 

Looking through the spell lists and monster manuals, Cold and Poison are common damage types that come up again and again. Entire biomes focus on them, with whole swathes of creatures dealing huge amounts of damage in these types. 

So a character with Infernal Constitution who happens to be venturing deep into the swampy jungle, fighting off hordes of feral Grung frogfolk, say, or invading an ancient temple atop a snow capped mountain, is going to be much safer than their poor, taking full damage from things, allies. 

Remember that Tieflings also gain resistance to Fire damage, bar none the most common damage type in 5e, as standard, meaning that a character with this feat has resistance against three of the most common damages a party might come up against. 

Resistance is generally useful on every character, too. Tanky types always appreciate another layer of defense, making their HP go even further and their job easier. 

DPS characters and casters don’t tend to be able to take the hits, often relying on positioning and their party to stay alive. Taking half damage in the times you misposition and eat a dragon’s breath might just be the difference between life and death. 

Advantage against Poison saves

In 5e, poison is split between two effects. Many poisons deal a big chunk of damage on a failed Con save. Infernal Resistance already helps with that, boosting Con and halving any poison damage a character might take.

The second part of many poison-based effects is the Poisoned condition, which can be absolutely brutal if it sticks. 

When a creature is Poisoned in D&D 5e, they have disadvantage on attack rolls and ability checks. Disadvantage forces a creature to roll two dice, picking the worst, whenever they make one of these rolls. 

This can utterly shut down certain character archetypes. A character relying on attacks in combat may as well set down their sword, as they’re going to miss far more often. 

Ability checks don’t sound terrible at first until you realize that every single skill roll in 5e is also an ability check. Inside of combat, expect most ability checks to be Athletics for grappling and not falling prone, and maybe some Arcana checks if you’re fighting spellcasters. 

Poison tends to be less frequent outside of combat, but traps and environmental hazards are common poison threats, and knowing the party has a character with serious resistance against it makes dealing with potential problems so much safer. 

Either way, adding all this together means failing a save against Poison tends to hurt. Infernal Constitution gives a character advantage (roll twice, pick highest) on Poison saves, massively boosting their chances of passing it. 

It’s also worth pointing out that many Poison effects are ongoing, ie, force saves every turn until a character passes. Advantage on every save means that effects that do hit home after a failed save are far less likely to stay that way

Key Stats

The Infernal Constitution feat gives a character +1 to their Con score. 

Ideal Characters for Infernal Constitution

Top Classes

Fighter – Tieflings make effective fighters, combining natural resistances and utility spellcasting, plus great stats, whether building Strength or Dex. The Fighter always wants to be tough, so stacking three resistances against common damage types, plus advantage against a common condition is a good way of doing that. Fighters also gain ASIs more frequently than other classes, so tend to have the space in their builds for lesser used, secondary feats like this one. 

Every subclass is going to be good. Battlemasters are, as always, incredible, balancing flexible abilities and raw power. Alternatively, lean fully into the defensive using Eldritch Knight, stacking the resistances from this feat on top of the warding arcana of the subclass to create a magically reinforced brick wall. 

Artificer – Who commonly uses poisons, is naturally surprisingly tanky for a casting class, and tends to have a grab bag of weird and wonderful skills that put them in strange places? A Tiefling’s natural spellcasting and interesting abilities also go well with a class whose whole schtick is basically “Int-Bard.”

The Alchemist subclass sounds like it might work well with this feat, but we’d avoid it, as it’s the weakest, most generic Artificer subclass of the four. Instead, if we were building towards this, we’d lock in an Armorer and become a literal walking tank, a juggernaut covered in magical metal, backed up by stacked resistances and a wealth of self-made magic items.  

Warlock – Warlocks don’t often need feats to be good at their core role, so have more space in a build for utility, sideline feats like this one. The class also only has middling defenses, (unless you take Hexblade and strap on armor) so a pile of resistances is always appreciated. 

Every Warlock subclass is good in its own way. We’ve already mentioned Hexblade. Fiends gain temp HP whenever they kill something, which is likely if you lean into building a DPS Eldritch Blaster. Undead Warlocks have a spooky transformation that adds a big chunk of temp HP, plus a fear condition rider to their attacks. 

Honestly, though, we’d probably go Celestial as a subclass. The healing it offers is significant, functioning as 1 + level Healing Words per day that don’t cost spell slots, plus gaining resistance to Radiant damage (nice) and temp HP (again) after resting. All of this adds up to a surprisingly tanky backline caster who can take a hit while keeping the party on their feet. 

Race or Subrace Choices

Infernal Constitution is currently only available to Tieflings. 

The Tiefling used to have 9 variant lineages, published in Mordenkainen’s Tome of Foes, which offered a wide range of stats and unique daily spellcasting options. These are now considered legacy content for official play, but you’re free to use them at your own tables. (And you should, because they’re awesome.)

Combos, Tactics, and Synergies

Complementary Feats

Poisoner – Much of the Infernal Constitution feat revolves around poison. Harvesting poison from monsters in 5e is inherently risky, and not dying on a failed check is a pretty sweet benefit. It also helps that the RP benefits of a poison wielding infernal-blood are just as much fun as coating weapons in venom and murdering everything down. 

Tough – While it’s terribly boring, +2 HP per level is a massive boost to a character’s total HP pool. If you’re looking to be as tough as possible then, well, take Tough. 

Sentinel – There’s no point being resistant to an enemy’s damage if they can just wander off and attack everyone else. Sentinel keeps enemies focused your way and adds some out of turn damage to sweeten the deal

Spells that Synergize

Armor of Agathys/False Life – Temporary HP doubles in effectiveness when you have resistance to damage. Combining this feat and spells is a great way to make both parts better. 

Absorb Elements – Unlucky enough to come up against an enemy you don’t have resistance against? Now you do, and you can slap back with your own elemental strike into the bargain. 

Strategies for Maximizing Infernal Constitution Effectiveness

Be more resilient

And not just by taking the Resilient feat. Hah. 

Resistances halve the damage taken from a source, which becomes much more powerful if the character has multiple ways of either mitigating damage or making their HP go further. There are multiple ways to get much tougher in 5e, spread across all of the defensive vectors in the game. Examples include:

• Increasing AC – Getting hit less often means taking less damage, and resistance means the damage actually taken is much less meaningful
• Gaining more HP – When you have resistance against damage, every extra point of HP essentially counts as 2. Increasing your Con score, taking the Tough feat, or finding a way to gain Temp HP (which does work with resistance) are all good ways to get bulky. 
• Save Proficiencies – Passing saves often halves damage taken, which does work alongside resistances to cut damage to a quarter. Proficiency in Con saves is particularly useful with Infernal Constitution, as that paired with advantage means that poison often stops being an issue entirely. 

Take the heat

If you’ve ever played an MMO, you’ll be familiar with the concept of aggro. 5e doesn’t have many direct mechanics that force enemies to focus fire; it’s mostly down to GM fiat. But keeping the enemies that can’t properly deal with you looking your way and failing to deal effective damage can make encounters much smoother, and helps keep the party alive and kicking. Here are a few ways to do that:

• Isolate – One of the simplest methods of keeping an enemy from attacking you is to keep them away from your allies. The most basic method is to literally just run up and stand in front of them, so they have to move around and past you to get to your friends, possibly eating an opportunity attack into the bargain. If you want to make this more effective, consider:
• The Sentinel Feat – We mentioned this feat above, and it bears repeating. Sentinel is possibly the single best method for melee characters to keep their chosen foe locked in place. If the enemy tries to attack you, hooray, you win. If they try to walk away, you get to make a reactionary attack, even if they take the Disengage action, and if that attack hits, they can no longer move. Sentinel only allows one of these special attacks (only one reaction per turn…) but this is one of the easiest ways to prevent enemies from going anywhere. 
• Prone and grappled – A prone enemy has to spend half their movement to stand up again, meaning even if they move away, they’re not going far. An enemy that’s prone and grappled can’t move at all until they break the grapple. And because of the way 5e works, it’s very easy for player characters to get much better at grappling than their opponents. 
• Spells and abilities – Many spells restrain, stun, or otherwise immobilize enemies. Considering how generally useful the Infernal Constitution feat is, most builds will have one or more ways of keeping their opponents in place among their class abilities and spells. 

Final Thoughts on Infernal Constitution

Infernal Constitution isn’t a bad feat. It’s just never going to be character defining, and probably won’t be many player’s first choice of feat. 

While defensive benefits are nice, Infernal Constitution’s resistances and saving throw advantage are specific, and in general, in 5e, it’s far better to focus on offense rather than defense. After all, dead enemies deal no damage. 

Still, though, if you’re a Tiefling looking to bulk up with a spare feat slot, or you know your campaign is going to heavily feature enemies and hazards that deal the damage types Infernal Constitution is useful against, what this feat offers is dependable and consistent. While it might not be priority number one, there’s still a lot of play in the feat, and in the moments when it saves a character’s life, you’ll be glad you took it.