Danger Sense + Blindsight = always advantage all the time?

[Greywander]

Danger Sense is a 2nd level barbarian feature that gives advantage on DEX saves so long as you can see the thing you're saving against. It doesn't work if you're blinded, deafened, or incapacitated.

Blindsight allows you to be aware of things within a certain radius, even if you can't see them with normal sight.

Blindsight should trump blindness, but it's unclear if it would trump deafness, too. I'm also not certain if you only need to see around you, or if you need to see the source of the effect, e.g. if you have an invisible spellcaster just outside your blindsight radius.

I'm trying to find ways to get advantage on saving throws, so this feature jumped out at me.

[Crgaston]

What have you come up with re: Advantage on saves?

Tremorsense would trump deafness. I don’t think blindsight would. It might depend on how you got it... is it a magical ability, or is it like a bat’s echolocation?

Regarding the origin being outside your blindsight radius, it would depend on the effect. Could you hear an incoming boulder in time? Probably. A spell effect? Maybe not.

Tremorsense would not interact with Danger Sense in the case of something like a Fireball, since it specifies that it only applies to things that are in contact with the same ground as you. There might be a monster ability that calls for a Dex save where it would apply, but I can’t think of one off the top of my head.

[Greywander]

What have you come up with re: Advantage on saves?
Not much, I'm afraid. I've been working on a guide of sorts to building up the defenses of a character, and I think I've exhausted most sources of advantage for saving throws.

Gnome gets advantage on mental saves versus magic.

Yuan-ti [Volo] gets advantage on all saves versus magic. Some class features and magic items grant this as well, although some only give it vs. spells, not all magic.
Keep in mind that some effects, like a basilisk's gaze, are magical, but not a spell. A dragon's breath, on the other hand, is not magical.
Yuan-ti are also immune to poison, which is a large chunk of nonmagical CON saves.

Vedalken [GGtR] gets advantage on all mental saves, period. Thing is, most nonmagical saves are going to be physical, not mental. Fear is a common one, though.

Danger Sense or Haste gives advantage on DEX saves. Potion of Speed works, too.

Rage or Enlarge/Reduce gives advantage on STR saves. Potion of Growth works, too.

Heroes' Feast gives advantage on WIS saves. Lasts 24 hours and doesn't use concentration, but costs 1k gold per casting.

Dungeon Delver gives advantage on saves vs. traps.

Warcaster gives advantage on concentration saves.

Boon of Perfect Health gives advantage on CON saves.

The most effective combo seems to be a yuan-ti with Danger Sense and Warcaster, but it will depend on what sort of character you're building. Rage is a lot less useful on a caster, for example, and Warcaster does nothing for non-casters.

[Lunali]

How exactly are you planning on getting blindsight in the first place?

As for sources of advantage, don't forget Kalashtar can have advantage on one wisdom save per round.

[Greywander]

Kalashtar has to use their reaction for it, though, and reactions are in high demand when it comes to defenses. Still, I do mention them in the guide I'm working on.

As for blindsight, it can be tricky. Rogues get it, eventually, but that precludes most other builds. I don't know if a few races might provide blindsight. I haven't done an in-depth search into sources of blindsight yet. I know one source that doesn't cost any build resources, but does depend on DM approval, would be the half-dragon template, which gives blindsight out to 10 feet. And I mean, honestly, this guide is already assuming you have access to legendary magic items like armor +3 and the Staff of Power, so we're probably past considering DM approval as long as it is within the rules.

[bid]

Not really.

Danger sense: "see"
Blindsense: "aware", "to hear"
If you hear something, you are aware but do not see it.

Opportunity attacks has the same language, as a few others.

[Lunali]

As for blindsight, it can be tricky. Rogues get it, eventually, but that precludes most other builds. I don't know if a few races might provide blindsight. I haven't done an in-depth search into sources of blindsight yet. I know one source that doesn't cost any build resources, but does depend on DM approval, would be the half-dragon template, which gives blindsight out to 10 feet. And I mean, honestly, this guide is already assuming you have access to legendary magic items like armor +3 and the Staff of Power, so we're probably past considering DM approval as long as it is within the rules.

Rogues get blindsense, which has an annoyingly similar name but is different. The only sources I'm aware of are the dagger of blindsight and a few magical items that give blindsight/truesight for a limited duration.

[Chronos]

In addition to rogue blindsense only being "aware of" instead of "see", it also only works on creatures, and doesn't let you perceive any other aspect of your environment (like, say, a Fireball that you want to save against).