This is one of my all time favorite games that I have played numerous times since the late 90s. The last time I played was post 2015 though I do not recall the exact year. Then I once again beat the campaign and for the 1st time ever played the Deepest Dungeon expansion (pirate). I also downloaded a huge pack of like 2000 user made levels and was working my way through them. I even nodded the game a little by editing the simple .ini files. That file should still be kicking around somewhere. From memory, I removed heal from warlocks and gave them life drain instead, plus teleport for max level. Orcs and barbarians gained heal at max level. Beetles gained freeze and dig to make them more useful. They did not have the AI to dig automatically so they could only dig while possessed, but that freed up an imp. I don't recall any other changes other than adding a bunch of conflicts between monsters and hero units to make it more difficult to mix them. Pretty much every hero unit got into fights with 2 monsters. I don't recall the exact details but thinking logically about it:

Avatars hated horned reapers

Reapers hated knights

Knights hated dragons

Dragons hated thieves

Thieves hated trolls

Trolls hated dwarves

Dwarves hated orcs

Orcs hated barbarians

Barbarians hated bile demons

Bile demons hated knights

Witches and wizards hated vampires

Vampires hated monks

Monks hated skeletons

Skeletons hated archers

Archers hated demon spawn

Demon spawn hated giants

Giants hated beetles

Beetles hated fairies

Fairies hated spiders

Spiders hated flies (like in base game)

Flies hated giants

Samurai (I don't recall this unit) hated mistresses

Mistresses hated witches

Warlocks hated vampires (was this in base game?)

Hell hounds hated fairies

Ghosts hated mistresses

Tentacles hated knights

Tunnelers hated imps

The first thing I did upon starting a map was set up the AI assistant to only help with combat, and keep it off unless a big fight was happening. When a big fight did happen I would turn it on for a few seconds, which automatically dropped my entire force into battle just as fast as the enemy AI could. This allowed me to go toe to toe with large armies and gave a massive combat advantage. It had to be turned off quickly though or it would repeatedly throw weak units back into battle. My job was to monitor the battle and pick up weaker and wounded creatures before they died. Sometimes cast a few spells to help, but I preferred to save gold. When designing my dungeon I first carved out a rectangular "wall" around the area I will use and made the imps fortify the entire outside perimeter before building anything. This prevented enemies from attacking me until I was ready but also lead to kinda boring play where I just sat around waiting for training as much as gold allowed before breaching my walls to let the enemy in. Not every map allowed this though, and those were more fun. Sometimes I save scummed and used sight magic to prevent digging into open areas. Next I made a tiny 1 space room with a locked door where I could lock up my imps. That way they would idly heal and not do stupid things like go off and get killed. Keeping control of the little buggers was often a pain in ass. The entrance to the dungeon proper was a fair sized barracks, which I used as a large guard room to station minions in preparation for enemy attack. This was where I wanted the fighting to occur, with strong doors to prevent spillover into the rest of my dungeon. I did not use the warband feature though. I really saw little point in it when I could go commando with a single possessed creature or use call to arms to take the whole army. Off this room protected by a door was a small graveyard, nice and close to minimize the distance my imps had to drag corpses. The door was hugely important so I could lock it to prevent corpse recovery, thus saving imps from doing stupid stuff like getting killed by a trap that just previously killed an imp. Another door in the barracks led to the rest of my dungeon, sometimes with a 2 door airlock design with an alarm trap in between. Beyond this was a massive open concept lair and hatchery. If enemies got past the barracks they would rile up sleeping monsters, but it was better to keep the fight outside of the lair so I could manually rotate units between the fight and sleeping to heal up. Some battles in custom maps were that tough. It was very important to have a single massive hatchery because creatures went to the closest regardless of how much food was there. Too often with multiple hatcheries I seen hungry minions getting angry waiting for chickens to spawn when they could have walked less than a minute to a different hatchery with food. I used to build tiny lair and hatchery inside the locked training room so a few creatures could train without needing input and without making me bankrupt with open access to training, but this led to the multiple hatchery problem so it was better to manually move creatures when they needed something. The training room always needed a door that could regulate gold loss. The size of training depended on how much gold was available. On maps with gem deposits I had a massive training room that never closed, sometimes even a 2nd room if necessary. I usually built the treasure room around the heart and behind in the far back to minimize the chances of enemies getting to it. Treasure and lairs were slapped down in whatever left over irregular shapes were around. Also in the back out of the way was the library. Somewhere I fit in a workshop, which was essential for doors. If the map did not have gems I built a massive workshop to support a trap selling economy. This was absurdly tedious though. Traps worked very well in the narrow corridor "wall" surrounding my dungeon but I did not use too many because I wanted to capture enemies rather than kill them. A couple poison or lightning traps just outside the barracks was ok. Boulder traps could be devastating and were best used against enemy keepers, but this was difficult to set up. The final section of my dungeon held the prison, torture room, temple, and a 2nd lair for vampires and skeletons, with a door separating it from the lair to help secure prisoners. Then lastly I had a small Scavenger room with a door so minions would not waste gold on it. Scavenging was mainly for stealing creatures from enemy keepers, which with the enemy doing it too usually led to me having only a limited selection of minion types while the enemy had all different units. I never knew that vampire scavenging allowed more minions to join from the portal. I also built outposts outside my main dungeon as the map progressed. Guard posts manned by level 10 skeletons easily held off annoying enemy imps while the skeletons only left for pay. Treasure rooms at gem deposits were mandatory, and more lair space was often needed as I converted enemies and created more undead. If necessary I built quarantine dungeons with lair, hatchery and tiny treasure room all behind locked door to prevent diseased creatures from spreading it around.

Since imps cost more gold to create the more imps I had, there was a limit to how many were worth having. They were damn annoying to keep alive. I usually trained some to level 3 for speed, especially when there were gems to mine. Sometimes I even let 1 get all to way to max level for sweet teleport, but it was terrible to lose leveled imps. Sometimes I possed an imp to mine gold then move it to the treasure room by hand to let the imps focus on more important stuff. I almost never used the slap. Flies were so weak as to be useless, and took forever to train. They were kinda useful for early scouting but I let them get killed or slap them to death myself. Beetles were only slightly better and still not worth using at all in any map with stronger creatures. My mod at least made it worthwhile to have 1. They also took forever to train. Spiders were the weakest decent unit and I usually ended up with 2 or 3. They tended to lose hp incredibly fast so I usually kept them in my hand to drop just long enough to use freeze, and not all at once so they could chain freeze. They were like having freeze as my own spell to cast at will. I did not like demon spawn much because they were solidly mediocre. If I had any I used them and hoped they morphed into a dragon. Dragons were the best monster tank unit that took ridiculous punishment but did not deal that much damage. They were also very expensive so I did not want too many. It was very rare that I had any do research but the option was there. Trolls were the best in the workshop and I avoided using them in battle unless it was low risk. I made sure to train them a little to get speed and some survivability. Orcs were better but still a fairly mediocre unit. My mod giving them heal made them much better at the front line tank role but they were still far behind dragons and bile demons. I never sought them out but kept them if I had them. Tentacles were somewhat tanky but took forever to heal; they were nothing special. Bile demons were a favorite of mine because of their tankiness without the high cost of dragons. I think they did better damage too. They did cause friendly fire with poison gas though. Them and dragons were the best ways to soak trap damage. Hell hounds were trouble because they had to be put on a leash or they would run off to get killed. Totally not good enough to be worth the trouble. I controlled them with the barracks or guard posts. Warlocks were a favoured unit of mine because ranged attackers could stack infinitely while melee was more limited; there was always room for more ranged dps. I had to monitor their hp and take them out of combat when needed. I usually built a big library for fast research and had like 12+ warlocks. Mistreses were another favorite because they were fast, deadly in melee and got ranged spells + teleport. They were the 3rd best choice to possess for scouting and killing, and were even more deadly under player control. The 2nd best unit for this was the vampire, which was also fast with teleport. Vampires were also very durable and would lose a level instead of dying, so surprise boulder traps were just an inconvenience. It was not really worth having more than 1 vampire though. Yes it was more power for pitched battles but vampires were ornery and would start vandalizing the dungeon and then leave at the slightest irritation. With fewer vamps it was easier to find the pissed off 1 to bribe, and their costs added up. Horned reaper was the most powerful and best creature to possess as a max level one could single handedly wipe out an entire enemy Keeper. I have slaughtered enemy units like nothing and destroyed their core with just a possessed reaper. Have to watch out for boulder traps though. Reapers required near constant babysitting though else they would permanently attack friendly troops. Training and temple were good ways to keep them occupied. Otherwise I sent them to attack the enemy they were near death then send them to bed, and repeat. They were a lot of trouble but their power was worth it. Summoning a reaper was the only temple sacrifice I bothered with. I remember 1 map where I had 5 or 6 reapers and managed to keep them in line. Worst case, lock them in their own quarantine area. Ghosts were not a good unit but their magic protection made them ok at mobbing spell casters. Having 1 decent level ghost with invisibility was very valuable for manual scouting. The rest could be thrown away in battle. Skeletons made up the bulk of my forces on most maps. I've even played maps where I had nearly 100 of them. Despite being a fairly mediocre unit, high levels give them lightning and made them nicely durable ranged dps. Most hero units (and enemy keeper monsters) were best sent to prison to turn into skeletons. Those with heal could still turn into skeletons by repeatedly throwing them into minions to be knocked out and brought back to prison. Eventually they would stave to death while heal was on cooldown. High level faeries and archers could be worth converting for ranged dps, while high level barbarians made decent tanks (even better with my mod). Knights, avatars, witches, and wizards were so good as to be always worth converting. Converting could take a lot of babysitting using heal or manually feeding chickens to the victims to prevent them from dying. I do think that converting the more powerful heroes was overpowered, especially the avatar who was even more powerful than the reaper.

Defending against waves of hero attacks and exploring intricate maps was the most fun. There were a lot of secrets to find in the campaign but the game was overall quite easy. Fighting other keepers though was a huge pain that required special tactics. Fighting pitched battles against their entire army was usually a bad idea, so I had several methods I used to win. Casting armageddon to force a pitched battle was a good way to gauge how strong they were, and if I could win that way then well and good. Most often they were too strong. Revealing the enemy dungeon was important so first order of business was to capture imps or other units for torture. Failing that I would do it manually with a possessed ghost, mistress, vampire or reaper. A simple but tedious way to win in a map with infinite gold was to kill all their imps with lightning and cave in spells. These spells were also good for finishing off weakened units after a quick battle. Spells were expensive so this tactic did not work when gold was limited, or their gem nodes and treasure room were too secluded to reveal. Possession to manually kill imps could also work. Avatars and reapers were so powerful that they could take on entire armies and inflict casualties before they needed to flee, so I had these units regularly on the attack or possessed. Sometimes I could even avoid enemies long enough to directly attack their heart. Many maps tried to protect against that by securing the heart in an out of the way fortified location, which just made it easier to kill the heart with a call to arms team of teleport commandos. Cast call to arms, drop all units with teleport (mistresses, vampires, and warlocks and I think wizards with my mod), then move the call to arms to their heart. If any creature walked close enough to be attacked it would trigger their entire army, so this did not work in dungeons where the heart was a regular thoroughfare. If all these tactics were not viable then it was time to break out the weapon of mass destruction; the disease spell. This spell was devastating and could potentially spread to friendly units, so that had to be planned for. All it required was a single cast on an enemy creature then trigger a fight so the enemies would all be bunched up and spread the disease. Then it was a matter of repeatedly triggering fights to not give enemy units the chance to rest, since the AI was not smart enough to quarantine or keep low hp units out of battle. If everything else failed then there was no choice but to fight pitched battles and inflict as much deaths as possible while preserving my own units. Knock their units out for capture to bolster my own forces if possible, and hold ground long enough for my imps to capture their rooms for selling as scorched earth tactic. This kind of conquest often took many cycles of attacking and resting up.

I want to try out KeeperFx at some point, possibly replay the campaigns, and play more of those player maps. This game is a legendary masterpiece that is always worth going back to.

9.5+/10