...could someone explain how did that thing move so fast? As far as I'm aware Arch-Viles have a speed of 160% (according to the wiki, it's probably outdated but I'd assume it's close enough, I doubt their speed has been tripled). Just before it killed me it was just outside my LoS, right above me, maybe one tile to the left.
It's hard to say since I'm not aware of the exact circumstances. An Arch-vile can't act fast enough to get two actions in between a ~0.23s attack (as this would require 400% speed, which is currently impossible), although the AI could have something to do with it. It's also possible that (given the amount of fluid around the area) you may had set off a barrel with the last attack, thus propelling the Arch-vile into view. Note that the ressurction action is actually instant, so that wasn't included as one of the Arch-vile's separate turns.
I've certainly had my share of losses because I got greedy with health conservation, so I don't fault you for being stingy.
...I know that in a situation like this
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..A.
I'm always safe despite the fact that I can see the enemy, but it seems that the moment they take one step away from the wall they can always see me no matter how far (horizontally in the example) away they are. Also it seems sometimes they can see me but I can't see them (I'd assume the scenario described above could be an example if the positions were reversed), it just feels odd that I'm being shot at despite the fact that I can barely see them on the edge of my LoS with Int.
Enemies have built-in artificial blind spots such that, even though you and the enemy have a mutual line of sight, they cannot use a ranged attack against you. The exact locations of these blind spots can be difficult to keep track of but you're pretty safe hugging a wall edge and shoot parallel to the wall. (In the example you give, if the enemy was about 5 tiles to the right of you and 2 spaces down, it should be roughly in a blind spot.)
There are also some unusual cases in which mutual line of sight is not obtained, allowing you to shoot an enemy from a literal blind spot (and vice versa). The most common occurance of a blind spot is when you and the enemy are in different rooms and on opposite sides of the portal that connects the rooms, as shown below:
..A.......
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Ultimately this can only be fixed by a refactoring of the vision code, which is supposedly one of the big changes we'll see in 0.9.9.5.
Do (some) monsters see further than I do or something?
Vision can vary among enemies. However, with the exception of the end-game bosses there is nothing that sees farther than you do. Lost Souls and Demons actually have less vision, meaning you can sneak past them at the edge of your own vision.
Also, I have no idea how to play without Int.
There are a few things to learn that makes the difference between a new player and an experienced one. They can be boiled down roughly into:
- Effective dodging tactics
- Corner-shooting and radar-shooting (scouting)
- Taking advantage of enemy blind spots
- Reacting to enemy noises
All of these are important in preventing damage to yourself, which is essentially the hidden goal of the game (simply put, you have to win if you don't die). Learning the weapons and builds and how they synergize properly is important too, but this list summarizes all of the more subtle aspects of the game that can really change the tides from a tactical persepctive.
I have no idea how the hell I'm supposed to kill the Arena Master on AoSh either...
Arena Master can be tricky on a shotgun-only run: I find that the most effective strategy is to wait for him to get close (as he often does these days) and position yourself in such a way that firing your weapon will constantly knock him back into the lava just outside of the starting room's exits. Either he attacks you and burns in the lava or tries to move out, and either way you're much better off than you were before. (You can try this same tactic to get rid of a lot of the enemies so that the Arena Master isn't constantly ressurecting them.)
Oh, and how do mod pack limits work? I grabbed wizkid so I could put some more power (and possibly technical) mod packs on that combat shotgun, but apparently you can't add anything into it after you turn it into a tactical shotgun.
Since you seem to read the Wiki, mod limits can be found
here. Specifically, assemblies cannot be modded except under certain circumstances as describes on the
assemblies page. If you're looking for power on a shotgun, I would suggest building an elephant gun or a focused double shotgun: both pack a very powerful punch. That aside, P3T2 shotguns are quite powerful on their own.
Also, welcome to the forums!