Hi folks! Been a long time since I've posted but I've had something on my mind for quite some time. Hope the interesting topic name attracts people heh 
So a while ago I was playing in a campaign where I played a variant human bear barbarian with shieldmaster feat. I was lvl 5 and some bad guy lobbed a fireball at me(well near me to be precise). First problem is that the DM said I couldn't benefit from my danger sense class ability(the one that says I have advantage on dex saves when I can see and am not deaf or incapacitated). His ruling was that the streak of light is simply too fast for a normal human to see. I disagreed, but since I'm a DM as well I don't make a habit of rules lawyering during the game so I let it pass and we kind of forgot about it later. Was I right or was he?
The second question lies between the interaction of fireball and shieldmaster itself. The fireball spell description says that the flame goes around corners. The shieldmaster feat states that if you succeed on the DEX save of an effect that causes you to take only half damage on a success, you place the shield between yourself and the effect, taking no damage(requires the use of your reaction). Because I failed my save I ended up taking half damage anyway(1st bear totem ability) so it really didn't come up, but since sometimes I'm a kind of a tounge-in-cheek nitpicker I was wondering if shieldmaster can even help vs an effect that circumvents cover. RAW I think specific beats general, right? So since ordinary cover doesn't grant any other boons than cover of sight, the shieldmaster's extra bonus overrudes the fireball's characteristic. Still funny to imagine but that's how I think it goes. What's your take on this situation?
And the third question is something that didn't come up but might have. If I didn't have a reaction to spend on the shieldmaster ability, but I succeeded on the DEX save. Would the damage from the fireball have been halved once or twice? Halved from succeeding fireball, then halved again from bear totem ability, or just once from one or the other?
If the streak of light being too fast for a human to react to is an argument for not getting advantage in the save, it's an argument for no one getting a save at all. Besides which, it's not the instant of the fireball shooting toward you that your Danger Sense reacts to, it's the events leading up to that: the incantations of the caster, them raising their hand, light gathering in their Palm, etc. Basically your DM's argument is bunkus.
Rules-wise yes, Shield Master's bonus to saves is just a bonus to saves. Fireball calls for a DEX save, so Shield Master applies. And again, if fireball spreading around corners was an argument for a shield not being able to block it, it would equally be an argument for no one getting a DEX save against it all all, since there'd obviously be nowhere to dodge to.
The halving of damage when you succeed at a save isn't resistance, the base damage of the effect that you take is just half what it would have been if you had failed. Resistance then applies, halving the effective damage of the effect. So you'd take a quarter of the damage rolled on the fireball, and half what anyone else who succeeded at their save would take.
One thing to note and something I always found bizzare about the Shield Master Feat: The shield -bonus- to saves (Including being used in the reaction bullet point) is limited to effects that target you and only you.
As for being hit with a fireball. Yes, you get Danger Sense. It's more or less limited to not being used against invisible attackers and what not. Yes, you can use your reaction for half, and then your bear totem kicks in. So if you got nailed by a fireball for 20 Damage. Your reaction eats 10 if you make the roll and your fire resistance from the bear totem eats another 5 , leaving you with 5.
But the grey area, is do you get to add your +2 (Or more if enchanted) shield bonus to your dexterity saving throw, if, say, that fireball only had you and only you in the AOE? Or is it limited to single target effects, like a Beholder's eye rays, etc?
BloodMoon666 wrote:
So looks like I was right on all accounts. Thanks for the confirmation guys. We both are quite new DMs(about half a year experience for him, and almost 2 years for me) and good friends so that's another reason I didn't start chasing justice during the game. That and it didn't really make or break the game either.
In any case thanks for the help.
Granville the AC bonus can't apply because if there's more than 1 target(you), then the spell probably asks for a saving throw, not an attack roll so your AC plays no part in the outcome.
Thanks for the compliment Noctaem :)
If the shieldmaster feat says "attacks that only affect you" I would take that to mean area of effect attacks are not affected. Although cones could be arguable.
The +2 to saves is for effects that only target you. "No damage in successful save" is always available.
There's no "DEX based attack roll," unless you mean an attack using Finesse or a ranged weapon, and Shield Master certainly doesn't have special rules for those.
Second bullet: "...you can add your shield's AC bonus [+2, usually] to any Dexterity saving throw you make against a spell or other harmful effect that targets only you."
Third bullet: "If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw...."
So you don't get the +2 vs fireball, but you can take 0 damage from it if you succeed and use your reaction. But, given the clarification on Twin Spell's restrictions, I would assume the +2 doesn't work on fireball even if you're the only target; the effect has to be only capable of targeting one creature. Can't think of an effect that would fit this description of the top of my head, though.
Macv12 wrote:
Disintigrate is a targetted dex save. And one that is very good to avoid.