The horror genre covers a broad spectrum of scenarios. What unites them are the feelings of mounting dread and powerlessness. Though D&D 5e is ultimately about acquiring power and beating the odds, you can still achieve a riveting horror experience through narrative and careful tweaking.
In older editions, there was a clear winner between Slow and Haste. In 5e, however, they are equally useful but in different contexts. Against a group of weak-ish enemies, you want to use Slow to control the battlefield. Against a single foe, Haste is better to maximize your action economy.
n 5e, grappling lets you keep an opponent from moving, forcefully move them, or even make them an easier target. You can drag them out of cover, make sure the rogue can Sneak Attack (depending on turn order), keep them Prone to give your allies advantage, and combo with Feats for extra nastiness.
determined by race, though class features can improve it. To move further on one turn, the Dash action, certain magic items, epic boons, feats, or magic can help.
1 gp is roughly 100 USD. Characters can spend money on lifestyle, transportation, toolsets, magic items/services—depending on playstyle—even on training and real estate. Often, adventuring is so lucrative that PCs hoard cool stuff in a way that feels unearned. But it doesn’t have to be so.
One-shots are different from regular D&D sessions. Time constraints force a more linear structure. Increased DM guidance is both necessary and expected. When running one, you need to roll with the punches players throw at you. Be careful not to over prep; one or two pages will do.
The key to running a great evil campaign is knowing that—at its core—it is still about creating a shared, fun experience. This means teamwork, respect, player agency, and flexible DMing. The campaign must be player-directed for the evil to mean anything unless you’re going for cartoon evil.
Booming Blade is not great. It fills a niche that makes it a subpar cantrip for most casters, but it has its uses for battlefield control. Best used by melee casters, like eldritch knights, arcane tricksters, artificers, warlocks, etc. Note that it doesn’t allow Extra Attacks for martial classes.
An opportunity attack is a melee attack you make against an enemy that you can see leaving your reach. You use your reaction to make this attack and must use whatever you have in your hand. Ranged attacks do not count, and some perks and subclasses can add extra utility to these attacks.
Ability checks and saving throws are both dice rolls used to decide your success or failure at certain tasks. Ability checks are for when you attempt a challenge; saving throws are for when you resist external factors—like spells, traps, or poisons. Though there’s slightly more to it than that.
To avoid killing in 5e, one can use magic, social skills, tactics, cunning, and nonlethal knockouts. There’s a rule for this in the Player’s Handbook (pg 198): when reducing someone to 0 hit points (HP) with a melee attack, you can choose to knock them unconscious—stable—instead of outright murder.