Auto-translated
Inferno, in my opinion, is along with Conflux one of the three most powerful castles in the game. It and Necropolis would be unsurpassed if not for the miserable start at 200% (at 160% it's fine). Either way, at 160%, Efreets are built on the first week in 99% of cases (1% when the exit from the city is blocked by monsters guarding an artifact or Pandora). At 200%, the chance is slightly lower; much depends on whether you get the right resources, but even then, Efreets are established in 70%-80% of cases. After buying four Efreets on 121, neutrals cease to be a problem. On the second week, all creature dwellings except for Devils + the castle are built at a waltz tempo (at 200%, sometimes without the castle). The third week should end with the construction of the cursed same palace of Devils, the municipality, and definitely the castle if it didn't happen on the second. That is essentially everything; we have sorted out the economy. Now let's move to the combat component.
First, let's choose a hero. This is difficult because this castle isn't provided with super-heroes. Nevertheless, there are a couple of interesting candidates here as well. If you want a mage, there is Adeine (Aiden) with a specialization in intelligence and starting wisdom. At high levels, this long-eared heretic possesses an almost unlimited mana pool. If he also manages to find a Dungeon with a whirlpool, the mana value can soar over 6000. The second mage relies more on SP than knowledge, specializing in magic. It seems to me that Zidar (Zaydar) will be weaker, as the percentage from magic is much lower than from intelligence, and this skill only works for offensive magic. However, after many games, I can say that a mage justifies himself only on L+U and XL maps; on smaller sizes, he simply doesn't have time to grow strong. However, Inferno also has several warriors worthy of attention. First on the list is Marius with his specialization in demons, which slightly increases their stats and gives (IMPORTANT!) +1 speed. This hero starts with advanced defense (armor), which is generally not bad. The second pleasant hero is the cute demon girl Pyre. She specializes in ballistae, having artillery and, importantly, logistics. This hero allows for a good start and even has the potential to grow into the main one. Sometimes it's worth paying attention to Ignat, who starts with tactics, specializes in imps, and accordingly brings them along. Not Shakti, of course, but if the imps are upgraded, he has decent breakthrough potential in the first weeks. I also want to mention Octavia (+350g/day), she helps at 200%.
But, taking into account all the above, I still want to say that the best hero for Inferno would be a recognized powerhouse from outside (Kreg Hack, Tazar, Mephala, Nila, Diplomats and Logisticians). Although, if none of the listed heroes wish to appear in the tavern of the underworld city, one can settle for Marius or Pyre.
Now briefly about the army. Let's analyze each unit separately and identify all their strengths.
• Lvl 1 — Imps/Imps
The basic version of an imp is a slow, frail, and weak unit suitable only for demonology. In the first week before Efreets appear, it is the main striking stack, then it plays the role of raw material. They should not be upgraded unless Ignat came from the start.
• Lvl 2 — Gogs/Magogs
Gog is a very mediocre shooter with low damage and low speed. At first, he helps the imps, and from the second week onwards, he is spent, being processed into demons. Not only does Magog offend his own, but they also require mercury for the upgrade. A generally doubtful unit. So upgrading Gogs is useless, and more often than not even harmful.
• Lvl 3 Hell Hounds/Cerberi
The non-upgraded doggy is an average unit with good damage and relatively decent speed. Nothing outstanding: it won't fail miserably, but it won't reach for the stars either. On the other hand, the Cerberus is one of the best, if not the best unit of its level, being on the same step as a Grand Elf, and sometimes even surpassing him. High speed, good health, excellent damage, and an unopposed strike combined with attacking three opponents at once elevate this unit to the heavens (cast them down into the deepest pit of hell?). Everything would be great if not for one "but". Their cages are not required for building higher Inferno units, and therefore dogs are rarely used as fighters, mostly being processed into demons. Is it worth upgrading them? No, unless a bet is specifically made on Cerberi from the start. At 200%, sometimes you have to build a strategy around dogs because there simply aren't enough resources for Efreets and they don't appear in the first week. However, doggies with cages in the stronghold, or perhaps in the castle, can become a decent breakthrough stack on 121.
• Lvl 4 Demons/Horned Demons
Demons are a super unit. Their characteristics are quite average and in small numbers, Horneds would be some of the worst units at their level, but no one has ever seen such small numbers... By the end of the month, these guys accumulate from 300 to 500 heads, and that is very serious. If you're lucky enough to catch diplomacy or a diplomat hero arrives (ideally Adele, though for demonic troops it's something...), you can push it up to 700. It is mandatory to upgrade them, as they become slightly tougher and one point faster, which is very good. And in general, a demon is an offensive stack after all, so he definitely earned the upgrade.
• Lvl 5 — Pit Lord
I don't even want to talk about the non-upgraded version of this troop type — grey mediocrity. But the red incarnation of the cave lord is a completely different story. This is the best unit at its level and one of the best in the game, upon which the main Inferno strategy is built. It is thanks to him that I place the demon abode on the same step as Conflux. By himself, he doesn't stand out: runs average, protected poorly, health is a bit low for a melee fighter, he hits hard indeed, but falls only on the way back from a counter-attack. However, no one will send them into a fight. Pit Lords will stand behind more combat-capable units and raise perfectly healthy demons from all the same rubble that comes to hand. The first three levels of their own and encountered castles along the way, as well as creatures joined by diplomacy—which I highly recommend grabbing at the first opportunity—give up their lives in order to be reborn as countless legions of demons. Thus, thanks to the red men with whips and the demonology they perform, Inferno receives colossal bonuses in the mid and late game.
• Lvl 6 Efreets/Efreet Sultans
An ordinary Efreet is a fast and strong unit that, appearing on 116-117, gives Inferno a pleasant and brisk start. An Efreet Sultan is noticeably quicker and slightly stronger than his non-upgraded brother, and he is so hot that anyone who dares to raise a finger at him receives a counter-attack from the fire shield. Is it worth upgrading? Definitely, because extra speed is never extra.
• Lvl 7 Devils/Archdevils
Devils themselves are a decent squad with satisfactory characteristics and an unopposed attack. Considering that they appear quite early (third week, and if you're lucky, you can slot them in on the last day of the second), Devils play their role in the army well. However, their full potential is revealed after the upgrade. Their characteristics become some of the highest at their level, surpassed only by Archangels. In addition, Archdevils get the third-highest speed at their level (after Phoenixes and Archangels), which combined with the unopposed attack makes them the second strongest level-seven unit. One downside — health is a bit low, but those are trifles; look, the Phantom Dragon has just as much health, and skills 1.5 times worse, and he doesn't complain.
In conclusion, I want to note that thanks to the demons raised via demonology, Inferno can take Utopias without much effort, not to mention canned goods and clues. Thus, the leaders of the underworld host are usually dressed according to the latest fashion, and a decent pile of gold jingles and clinks in their pockets. Combined with a huge army of horned and winged ones (Angels and Wyverns), these guys are capable of much.
I hope now no one considers Inferno weak?
P.S. Everything above is based on tournaments in which the strongest players from Russia and abroad participated, as well as on my personal experience accumulated over 14 years.