YMMV / Warhammer 40,000: Gladius

• Demonic Spiders: It just wouldn't be Warhammer 40,000 if there weren't an alarming number of nasty things with a dozen new and exciting ways to make your troops die horribly roaming around. Just about anything you encounter that isn't a Kroot Hound requires either human-wave tactics or a decent chunk of research to properly deal with, and you will run into them long before you have weapons capable of fighting back efficiently.
  • Enslavers, those damnable gasbags guarding Old One Relics, are surprisingly tough, can fly, passively drain the morale of nearby units, and can Mind Rape your low morale units into obeying them. Killing them can be a chore (and one Imperial Guard quest spawns a crapload of them over the map, which need to be killed to progress), requiring about four attacks from basic infantry, which you have to do if you'd like your units back. Necrons get a tiny bit of leeway, for even though they are inexplicably not immune to being controlled (despite their anti-warp presence and lack of souls), they take a while or even never go down the morale threshold for control, which means the Enslavers must generally settle for "only" using their claws, which deal Rending damage, so enjoy watching half your Warrior squad die in one shot. For added fun, they can easily be found wandering into your starting area as early as turn 3 (if you happen to start close enough to a Relic). These guys are why you research grenades the moment the game starts.
  • Catachan Devils, scorpions as big as tanks and half as friendly, they pack a wallop and are lightning fast over difficult terrain. Which, of course, is also where you find their nest, that you need to knock out if you want to stem the flood of monster bugs eating your men. Even low level Fiends can lop off half of a Tactical Squad's health in one blow while requiring anti-tank weapons to do anything above Scratch Damage, and even then require several hits to go down, or else they'll just skitter out of sight and come back a few turns later at full health and as hungry as ever.
  • Kastellan Robots come in two flavors: incredibly deadly, and destroyed, with a very large amount of work going into turning them from the former into the latter. They have hit points and armor levels on par with mid-game defensive fortifications with the firepower to match, so even one of them can bring an early game advance to a dead stop with a pretty good chance of defeating you. You will, however, almost certainly never run into just one, more likely four or more, which is when you get to watch them rotate themselves through the front line as they take damage, swapping in fresh units while the bot you just spent four turns grinding down waltzes away. This is when you find out they're being repaired on the fly by units of Cybernetica Datasmiths far faster than you can damage them. Now take all of this, and roll the dice on having a couple of them come barreling into your deployment zone on turn 5.
    • Fortunately, if you are playing as the Adeptus Mechanicus DLC faction, running into a horde of rogue Kastellan Robots can actually be a boon if you brought a decent amount of your own Datasmiths, as they are capable of reprogramming the Robots to your side. Unfortunately, the rogue, hostile Datasmiths that accompany said Robots are also capable of hacking your own ones back, so be sure to try to eliminate them beforehand, but good luck doing that without taking too much damage in the process.
• Difficulty Spike: The faction quests come in 4 parts. Part 1 and 2 are usually some kind of fetch quest or earn enough resources, do research. The third part of the quest usually involves dealing with some minor invasions. Before you go any further, it's recommended that all the other factions are wiped out and you control all the map's resoures and build up an epic army because you then deal with a full-scale onslaught. Additionally difficulty in the final quest varies by race - with the Orks perhaps getting the rawest deal as they could end up facing Space Marines, Astra Militarum and Necrons at the same time .
• Funny Moments:
  • As per usual, the orks get most. The keys to the space hulk are described as having fuzzy dice attached, some pilots quote Apocalypse Now, Ogryns describe orks as tough, good-looking and clevver ("like us")...
  • For Black Comedy, the flavor text for the Imperial Guard edicts makes it clear you're working/starving your population to death to increase production... except the population growth one, which tells hab-block supervisors to encourage connubial behavior.
• Game-Breaker: In high-resource games, the Necrons's Rapid Rush ability (paying influence to have a unit ready on the next turn) becomes exceedingly powerful, because it means you only need a single production building (and it doesn't even need to be staffed!) to pump out a unit every turn, freeing up tiles for, say, influence-producing buildings. Enjoy your unbroken stream of Obelisks sliding out of the city every turn.
• Goddamn Bats: Many of the Neutrals, Critters, and Creeps early on:
  • Kroot Hounds come in large swarms that do just enough damage that you can't outright ignore them, but force you to spend precious actions killing them. They also have the "Infiltrate" trait, which allows them to run up to your units without ever being targeted by overwatch, so clearing them out is a monotonous slog even compared to other creeps. Early game, they're a legitimate threat to isolated units, but they quickly become roving chunks of experience that like to liberate your outposts when you're tied up halfway across the map.
  • Vespid Stingwings. Since they have ranged weapons (despite only having a range of 1), they're among the few creeps that can perform overwatch attacks to punish careless exploration. This makes them a particular menace in areas full of vision-obscuring forests and ruins, where your infantry will blindly bump into packs of stingwings and lose chunks of health. They're also nearly impossible to pin down, as they ignore forest/ruin movement penalties and aren't stopped if they pass adjacent to any of your own units.
• Good Bad Bugs: Some players with only the base game have noticed that starting a game with all tech researched lets them use DLC-only units like the Chimera or Centurion Devastators.
• Low-Tier Letdown: The Orks and Tyranids get a lot of online flak because of how bad they are from early game to late game. The Orks start off with weak units, need to keep morale up or they start dying and require a lot of influence as an extra resource, their late-tier units are powerful but still not on the scale of those of the Necrons and Astra Militarum plus they're a big drain on the Ork economy. Tyranids have weak units and have a need to keep many of their units close to a synapse creature or face major penalties (such as constantly bleeding off health or having their movement cut down). Even Tyranid late-stage units are rather weak with the exception of the Lictor. The saving grace for the Tyranids are powerful heroes and being the fastest ground force in the game.
• Visual Effects of Awesome: Unit animations vary between good, average or bad, but many users have noted that the animations for the Canoptek Spyder is considered one of the best.