YMMV / Underrail

• Awesome Music: The soundtrack by Josh Culler is a diverse set of mesmerizing ambiance that ranges from relaxing to foreboding, giving the locations a sense of immersion.
• Base-Breaking Character: Rahm-Umbra, a Godman who you officially meet in the Deep Caverns or potentially earlier. Players either find him to be Creepy Awesome or a Mr. Exposition who derails the plot to Info Dump you.
• Broken Base: In July of 2020, the developer released a large, sweeping change to Psi builds with the intent to bring them more in-line with other builds due to Psi being somewhat of a Game-Breaker. While the nerfs didn't completely tear apart Psi, they certainly nerfed it to the point where Psi builds are no longer the strongest type of build in the game, with many Psi-purists decrying these changes as taking away the fun of the builds somewhat. The biggest change is that bringing multiple abilities into your build from different Psi schools incurs a very heavy penalty, meaning that Psi players are now forced to pick one or two schools and stick with them rather than become a Master of All.
• Complacent Gaming Syndrome: On lower difficulties, this is somewhat downplayed. Every single build a person makes has to be smartly made to even survive the midgame, but following that the rest of the game is rather susceptible to multiple different buildpaths and an unoptimized character. On the higher difficulties, this is enforced, and it's difficult to progress past even the early game without managing to construct a gameplan and the knowledge necessary to enforce it. Whether you're going "Tin Can", long range sniper, Psionics or anything in-between, you need to have a clear goal in mind for the endgame of your character and be aware of your limitations more than any other CRPG.
• Demonic Spiders: And how! The game does not pull any punches when it comes to deadly enemies, often forcing you into unconventional tactics to deal with them.
  • Azuridae beetles hit hard for early-game characters, especially when in groups where they gain access to more powerful abilities, but it gets worse when you face the Azuridae Goliathus, a far larger, far more armored and far more deadly variant of the psi beetles that deals incredible amounts of damage with even deadlier abilities at its disposal, while starting every combat encounter with Pseudo-Spatial Projection, allowing it to dodge a large amount of initial attacks until all the clones are dispelled.
  • Enemies with Thought Control are widely regarded as being the most infuriating variant of psionic enemies to fight, either because they use Neural Overload or the dreaded Bilocation, summoning an enemy that is invincible against conventional attacks, has a very low AP cost for attacks, and deals massive irresistible damage against characters that do not immediately run away for several turns, on top of body-blocking characters and triggering laid traps with no consequence. Enemies with Mental Breakdown (an ability that doubles any Thought Control attack against affected characters) will often cast it first and then summon two dopplegangers, making short work of players.
  • Crawlers are where the game decides to abandon any pretense of fairness. They are the Master of All the game takes great pains to prevent players from becoming; they have no real weaknesses to speak of, other than cheesing them with bear traps. They have a two-turn stun, heal 20 HP every single turn unconditionally, are almost impossible to legitimately detect before they reach you, will nearly always get the first strike, do very high damage, can teleport while stealthing, and higher-level variants will prevent the player from using any medicine, including antidotes, forcing you to eat the two-turn stun.
  • Coil Spiders use electric attacks that can stun and easily kill you if you do not have any electric resistance, and they can be dealt with by turning on your shield to protect against electric attacks. Sounds simple, right? Enter the Greater Coil Spider, which on top of Electrokinesis also casts an EMP attack that will drain your shield (and every electronic device if playing on Hard and above), making you vulnerable to their attacks. On top of that they live in heavily-webbed places full of hidden web traps that will most likely spell your doom if you fall in one, as it will not only stun you but also alert every Coil Spider in the area.
• Difficulty Spike: The early game up to Junkyard is fairly easy, but Depot A is very challenging on a first run. Numerous traps, Infected Dogs that stunlock you, Mutants that deal tons of Bio damage, and a mazelike design all make Depot A into the most difficult part of the game. This is an enforced example, since players who fail to beat Depot A will struggle to complete the rest of the game, which is similarly challenging but to a lesser extent.
• Disappointing Last Level: The Deep Caverns is much more of a slog than the rest of the game, with even more backtracking than the rest of the game and forcing you through endlessly respawning enemies. It was bad enough that a patch added several ways to Dungeon Bypass a lot of the areas for those with high skills. The epic Final Boss does make up for it somewhat.
• Ensemble Dark Horse:
  • Al Fabet, for being an Affectionate Parody of RPG players who take anything not nailed down.
  • Vivian Young, the player's Mission Control when following the JKK questline. A Plucky Girl with a unique character model who is Killed Offscreen by JKK for being a coretech double agent. Many players will avoid JKK altogether to prevent her death.
  • Dan, the laid back guard at foundry who will help you fight the beast solely due to boredom. He can also be recruited to help Gorsky take out the Black Crawler gang.
• Game-Breaker: Underrail takes a lot of care to make it so that you can't be a Master of All, as every build has their strengths and weaknesses, but psi used to be one before it was nerfed in 2020. While pure psi builds were massively nerfed, builds that only partially used psi were made even stronger.
  • "Burst Fire" builds are builds that use More Dakka with the Burst Fire ability, which benefits a lot from feats such as Spec Ops (reduced action point cost), Suppressive Fire (applies debuffs to every enemy caught in the cone of fire), Commando (a free Burst Fire attack after killing an enemy with a Burst Fire attack), and Expertise (bonus damage per bullet equal to your level, up to 20), allowing you to kill entire groups of enemies in one or two turns with the only downside being that you need plenty of ammo and repair kits.
• Goddamn Bats:
  • Burrower Spawn, always in the company of their toxin needle-spitting parents, who are also eager to keep making more.
  • Expedition brings us Locusts, which pour out of giant hives in swarms and spit debilitating poison needles at a distance, which "infest" you and make baby locust spawn from your flesh.
• Paranoia Fuel: Generally speaking, walking through the long abandoned tunnels. Once filled with people using transportation, the corridors are dark, silent places that are accompanied by disturbing ambiance. What brings up the paranoia is that they can be filled with stealth assassins, crawlers that can go invisible, and other enemies that will use the element of surprise to ambush you.
  • In the expansion, Handmaidens and Strongmen are disguised as statues when not in use and will spring to life when you pass by them. Even the 12-foot tall Naga Protector looks like an innocuous part of the scenery before it activates.
• The Scrappy: Coral. A fortune teller and travelling merchant who can read your palms. Her inventory mostly consists of low-quality hopper skins and she offers you the incredibly useless charms, which do not tell you what their effect is, sometimes have a negative effect, and work at random. The really infuriating part is that the far more useful and far cooler mutie tattoo artist, Booth, will not appear in games where Coral does and there is no way to tell if your game will include Booth at the start because coral only shows up randomly at each bar. Fans won't even complain about using a cheat engine if it is used to check if you will get Coral at the start.
• Slow-Paced Beginning: The early game is widely considered to be the worst part of the experience. You're relatively weak, have to use mediocre weapons to get by, the majority of encounters will kill you easily, and if you don't build properly the game can be extremely difficult. Once you clear Depot A, the rest of the game becomes smooth sailing as great gear, better weapons, and useful crafting supplies begin flowing your way. As well, this is around the point where most builds begin to solidify themselves, meaning combat generally becomes far easier.
• That One Boss: In a game full of these, the final boss of the Arena deserves mention. A fist weapon wielder with many feats under his belt such as Bone Breaker, Cheap Shots, Yell, Combo and Conditioning, as well as huge combat stats including defensive ones, who starts combat at a very high initiative by throwing a net at you that is very likely to land before rushing you in one turn and likely killing you in one turn, and to top it off massively decreases your combat stats by Yelling, making him extremely difficult to hit with regular weapons, while most grenades barely do any damage against him. Expect to reload a LOT.
• That One Level: Depot A is the part of the game most people get stuck on. The place is huge, filled with several powerful mutants and is laden with traps everywhere. Infected Dogs act as serious roadblocks to your progress and the sheer amount of enemies coming at you at once is impossible to deal for certain builds. Without careful preparation it is quite literally impossible to beat this section, since you either require a ton of powerful explosives to deal AoE damage to thin the herd, or else tons of bear traps to create a wall between you and them, allowing you to pick them off one by one. Either way this place is a serious drain on your resources, especially if you came here without any points in the Traps skill.
  • The Nexus of Technology in the Black Sea pits you against several dozen Strongmen and Handmaidens, NFT androids with a whopping 70% reduction in mechanical resistance and high cold and heat resistances. This can be nigh unbeatable if you don't have access to mountains of W2C rounds or Chemical Pistols. Anyone trying to do a pure Psi or melee build will also be absolutely stuck as robotic enemies are immune to thought control and melee attacks incur additional reductions in damage from armor, though at least the latter has access to electrical tipped weapons and Energy edge blades if they had the foresight to spec into crafting.
  • However, all of them pale in comparison to the Fetid Marsh. Filled with Goddamn Bats in the form of locusts as well as [[Demonic Spiders Serpents of every type]. It also has a confusing layout that is difficult to navigate and large uncrossable water ways that can put all the serpents just out of reach of most weapons.
• They Wasted a Perfectly Good Plot: The Oligarch questline is required to proceed with the main plot, and the Oligarchs are a major part of Core City's backstory, but the game does very little with it. They award you with a house for your trouble and they allow you to use the company store to obtain high-quality gear but there is very little else you can do. There is also no way to unravel the mystery of the Coretech Warehouse attack, though you can gather enough Story Breadcrumbs to reveal Ola, the JKK agent is behind it. The Praetorian Questline even tells you to look for a motive behind the attack, and allows you to learn from Jon the Beautiful who may be behind it, but gives no additional dialogue when you report in. Trying to Take a Third Option and bypass the Oligarchs entirely through Phreak is considered even more lackluster.