l have a character who's backstory has them being obsessed with learning and gaining knowledge,and with them being a 120 year old elven wizard they would have lots of time to learn stuff. Given this information,would you allow the character to always have advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire from a retired troll hunter?)

side note,would you let them know more then just the normal amount of languages? the character knows Common, Draconic, Druidic, Dwarvish, Elvish, Infernal, Orc ( non common/elvish learned by being taught by dragonborn,tiflings,dwarfs,half orcs and druids) this has been stated in their backstory. (they also plan on learning more,like thieves cant from the party rouge and any other languages they can)

edit 1: thanks for the feedback! some things some of you seem to have not seen is the part where l said "advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire or something?"

l am not asking if they would get all checks forever(though given the questions name l can see the confusion),but just on stuff they would have realistically have read about in the citys library/mage guild/heard about from travelers/whatever.

also the languages are from a combo of things like sage background and other stuff free with the character maker plus one or 2 added (which l could make make them take the linguist feat for,so thanks for bringing that to my attention!)

edit 2:you have all made great points,thanks! l am somewhat new to dnd,so the things stated below are a big help! thanks! the player this character belongs to knows that asking for perm advantage is dumb and now has a better understanding of the game! again,thanks!

Edit 3: short answer:no. long answer: their backstory explains why they have perks/feats/ect but does not give any real bonus.

No.

You're effectively saying "My character is REALLY good at knowing things, like...better than other people at knowing things.  Can I have advantage on knowing things?"  That's somewhat equivalent to a fighter asking for permanent advantage on his attacks because "I trained really hard for a long time to get good, like REALLY good, at hitting things.  I can totally have permanent advantage on hitting things, right?"

Nope.  Your character's expertise is expressed in having proficiency with the given skill, and with having a higher than normal ability modifier as well.  If a subject comes up that's specifically related to your character's backstory, a DM might give you advantage for that particular check.  Knowing your local region's history and legends well does not entitle you to permanent advantage on all knowledge checks forever.

As to languages, maybe double-check with your DM before saying "my character knows seven languages instead of two because backstory."  Because that's the sort of thing a good DM is going to examine real closely before letting it through.  There's a feat for that, and while I heartily endorse allowing players to select one fun, flavorful backstory feat like Linguist before game start, it's still something the DM has to okay first.

Exceptional competence with particular skills is covered by Proficiency or Expertise.

Backstory does not generally grant mechanical benefits -- rather, it explains benefits (e.g. it won't give you a feat, but may explain why you have a feat).

No, because advantage is generally conferred by a situation. For example, you flank a guy, that gives you an advantage on the normal rolling rules. But I would not just give blanket advantage to a skill under all conditions.

No. To take history as an example, even if I know a lot about the history of my city (enough to rate advantage on a roll about it), that doesn't mean I know much about the history of anyplace else, or even the history of my city during a different time period. The knowledge categories are so broad, its impossible for someone to be that level of expert in all of them. If you wanted to give them advantage on a specific roll, because it could plausibly be something they studied in their backstory, that could work, but it needs to be case by case. 

As far as the languages, that's maybe not game breaking (like permanent advantage would be), but you are giving away a chunk of the linguist feat for free. I'd tell them if they really want to show their language ability, they should take the feat. Make the investment to get the reward. 

It's kind of a slippery slope you're on here, giving things away because someone wrote it in their backstory. You're setting a precedent that could easily be abused in the future. Also remember, this is (I'm assuming) a 1st-level character. You don't start out being able to do everything, that's the (well, a) point of the game is to gain power and grow as a character. It would be like a1st level thief being the head of the thieves guild. It doesn't work like that. You need to earn it.

Not agreeing with either side here, but one thing to consider is that the reason existing backgrounds give you the bonuses they do is because you've spent the required amount of time to gain them. They aren't instant magically-acquired things, but rather skills you've spent your entire/substantial part of your life gaining. 

That being said, there is no reason why a background couldn't allow a player to learn more than is given, but also no implied reason it must be allowed either. You spent your life learning about things? Well, that's already covered by the existing background benefits.

Quote from Pantagruel666 >>

Exceptional competence with particular skills is covered by Proficiency or Expertise.

Here we go. If the story lent itself to your character being an expert with a skill, the DM might give your character expertise with that skill. Later on in the game, that would actually be stronger than advantage anyway.

No.

The class features and backgrounds already take into account the fact that your character is extra good at things.

Remember - the BASELINE isn't an adventurer, it's a commoner with 10, 10, 10, 10, 10, stats. For example, going through your requests:

Quote from DnDNewper>>

l have a character who's backstory has them being obsessed with learning and gaining knowledge,and with them being a 120 year old elven wizard they would have lots of time to learn stuff. Given this information,would you allow the character to always have advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire or something?)

This is ALREADY REPRESENTED mechanically. Presumably by being a wizard you've picked INT as your best stat and have a +3 bonus to it. The sage background gives you proficiency in Arcana and History. The wizard gets to pick two skills from Arcana, History, Insight, Investigation, Medicine, and Religion. And of course, wizards get spellcasting, with a spellbook and cantrips.

Those are all things that your wizard knows because they were obsessed with learning, gaining knowledge, and spent their entire life on it.

side note,would you let them know more then just the normal amount of languages?

The "normal" amount of languages for a person is one, maybe two. Common - and possibly one racial language. Common and Draconic for a dragonborn or something, common and Elvish for an elf.

You as an elf would already know elvish and common. You could get one more as a high elf, and two more of your choice from the sage background.

That would put you at THREE more languages than "normal". Your backstory - that you spent a lot of time studying - is represented mechanically by the background and racial abilities already.

the character knows Common, Draconic, Druidic, Dwarvish, Elvish, Infernal, Orc ( non common/elvish learned by being taught by dragonborn,tiflings,dwarfs,half orcs and druids) this has been stated in their backstory. (they also plan on learning more,like thieves cant from the party rouge and any other languages they can)

The game provides mechanics for learning more languages - downtime activities (if you have a long enough break between adventures, you can spend it learning things) or feats.

edit: thanks for the feedback! some things some of you seem to have not seen is the part where l said "advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire or something?"

The DM is obviously free to make checks easier if they think you would just have that information based on who you are (or even not require a check at all).

I don't see why "a troll's weakness to fire" is something that a scholar that spent their life learning spells and languages would be especially likely to know, though...

l am not asking if they would get all checks forever(though given the questions name l can see the confusion),but just on stuff they would have realistically have read about in the citys library/mage guild/heard about from travelers/whatever.

also the languages are from a combo of things like sage background and other stuff free with the character maker plus one or 2 added (which l could make make them take the linguist feat for,so thanks for bringing that to my attention!)

I think part of the reaction to your post is that you're just trying to make your background give you skills that are nonsensically broad. You say your character "is obsessed with gaining knowledge" and would have lots of time to "learn stuff". What kind of stuff? It sounds like you mean literally everything. You're trying to write into the backstory that the character not only spent all their life studying spells (to become a wizard) and languages (to have more languages) but also medicine, history, flora, fauna, religion, *everything*.

And you want your backstory to give mechanical bonuses to all that, beyond what existing character creation provides.

If you skip that mechanical bonus part - just take the rules as written, make a wizard with them - then your description basically fits the character perfectly! An elf wizard who's spent a century studying is basically, like, the stereotypical wizard! And of course, lots of DMs will listen and will give your character the info they think you would already know (e.g. troll weaknesses if your character had some reason to fight trolls in their background, sure).

If its a niche area I'd grant advantage. If its something common knowledge because its his hometown then rolling wouldn't be necessary imo, and a normal history check will do if its something less known.

For example, a druid in my last campaign was fanatical about mushrooms, so I let him take nature checks with advantage only when identifying mushrooms or their properties. They didn't gain advantage on "everything there is to know about the forest" checks though.

I agree with ftl on this. Everything stated in the OP is already accounted for in the game by taking the right stats, skill proficiencies, class, background, and feat options. There is no need to gain extra beyond this.  

For example, "and with them being a 120 year old elven wizard they would have lots of time to learn stuff" -- The game already accounts for this in the rules for making up elven characters. It's not as if the game designers didn't know elves who were 120 years old would have lots of time to "learn stuff." They would assume it. In fact it even says in the Elven racial description, and I quote, "Since they are so long-lived, they can enjoy centuries of exploration and discovery." 

So, the game designers already assume an elf character would be 120 or more years old, and would have all those years to "learn stuff." Given that assumption, they wrote up elf characters as they did, giving them all the advantages the designers thought would, within the needs of game balance, be reasonable for 120 year old (or older) adventurers. You therefore cannot (unless your DM decides to go outside the "rules as written") impute more skill, knowledge, or ability to your elf character just because he or she happens to be an elf. All the things a 120 year old elf should have, be, or know, is already represented in the elven character racial stats, bonuses, and so on. If the game designers wanted that 120 years of experience to give you "advantage on all skill checks" they'd have written that. If they wanted it to give you +3 languages, they'd have written that. Living 120 years and then going on adventures does not make this character an above-average elf -- it makes him or her a typical elf. Therefore, all you get for being a 120 year old elven adventurer is the racial stats already provided in the rulebook.

Now, wanting to be an especially "scholarly" elf is possible, but you just pick the appropriate background option for that (sage, as stated above). The designers also balanced this background option against the others and gave all Sage characters the appropriate in-game skills and abilities that someone who is a bookish person would have. This background provides you with the two extra languages your "bookish elf" character would have over a regular elf, and the additional proficiency bonuses that you would need to be a bookish elf rather than a regular elf. 

The goal of writing up a background is not to give a character extra things beyond what the game already says you can have; rather, it is to provide context and an explanation or justification for why your character has those game mechanics. For example, your backstory write-up explains why you became a wizard, not "why your wizard should have more spells than the rulebook says." And your backstory write-up explains why you took the Sage background, not why you should have "advantage" on all the skills in that background even when the rules don't say you do.

As a side note, I wonder what kind of memory do elves in D&D have ;-)

 I rather liked the Capaldi-era Doctor Who season where a girl was turned immortal but she had to literally keep a library full of tomes of her life's events and people she had met because when you don't have a perfect recollection, you tend to forget stuff that happened to you decades ago ;-)

According to M's Tome of Foes, "From birth, elves don’t sleep but instead enter a trance when they need to rest. In this state, elves remain aware of their surroundings while immersing themselves in memories. What an elf remembers during this reverie depends largely on how long the elf has lived, and the events of the lives that the elf’s soul has experienced before."

This interpretation of elves has each one being a reincarnation of previous elf beings going back to the beginning. Early in life a lot of their memories actually come from their past lives. These memories fade as they reach adulthood and then return in old age (after 300-400 years old) and after returning eventually these memories sort of "take over" and the elf dies naturally. The soul then returns to Arvandor, and the process starts over.

This formulation (which I personally detest, and would certainly not use in my own game if I were DMing in 5e), implies that a 120 year old elf would perhaps not know all that much more than a young adult human, because for many of those 120 years, their memories were not really their own, and so they had to sort out past from present. Since, again in this formulation, their past life may have been lived on another world and not their current one, those memories might be of zero use in the current campaign.

Again, all of this was known to the writers of the PHB and other supplements and is "baked into" their write-ups of the elven defaults and the sub-races. Thus one cannot use the justification "I am an elf" to provide anything more than what the rules say you get.

Quote from DnDNewper >>

l have a character who's backstory has them being obsessed with learning and gaining knowledge,and with them being a 120 year old elven wizard they would have lots of time to learn stuff. Given this information,would you allow the character to always have advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire or something?)

side note,would you let them know more then just the normal amount of languages? the character knows Common, Draconic, Druidic, Dwarvish, Elvish, Infernal, Orc ( non common/elvish learned by being taught by dragonborn,tiflings,dwarfs,half orcs and druids) this has been stated in their backstory. (they also plan on learning more,like thieves cant from the party rouge and any other languages they can)

edit: thanks for the feedback! some things some of you seem to have not seen is the part where l said "advantage to checks related to history,wildlife,religion, ect (that they would realistically find in their home city? like about a trolls weakness to fire or something?"

l am not asking if they would get all checks forever(though given the questions name l can see the confusion),but just on stuff they would have realistically have read about in the citys library/mage guild/heard about from travelers/whatever.

also the languages are from a combo of things like sage background and other stuff free with the character maker plus one or 2 added (which l could make make them take the linguist feat for,so thanks for bringing that to my attention!)

 My shortest possible answer.

120 is young for an elf.

2. I could have a elf, timeless body. Be 730 years old. Who is actually closer to 7000 years old.

maybe if this elf was really thousands of years old, with a keen mind feat, then, maybe the adv on things for no reason sure.

but otherwise no. Because you are literally diminishing built in skills and mechanics designed for classes and races and backgrounds specifically. Just for a characters. Not exactly elaborate or detailed backstory, but then just wanting to be able to superhero the entire session.

edit: read FTLs’ post. Pretend I quote it again here. And bold and italicize his points. As FTL nails it.

Quote from BioWizard >>

No, because advantage is generally conferred by a situation. For example, you flank a guy, that gives you an advantage on the normal rolling rules. But I would not just give blanket advantage to a skill under all conditions.

 Flanking used to be a rule. It’s not in 5e. But is usually houseruled to be there still. 

So, you wanna be so OP and you don't know how to ?????

P.D. : If the DMs allows this, then it's the perfect time to claim for those skills that were lost..... in time.... 

In example :

     * Mercantilism  ( where is it, when we mostly need it )

     * Navigation ( or at least cruising )

     * Astrologic knowledge ( or how to know where everyone is on this Planet, or Plane of existence )

Flanking is an optional rule, pg. 251 of the DMG. Quote, "If you regularly use miniatures, flanking gives combatants a simple way to gain advantage on attack rolls against a common enemy." There are then six (6) pictures at the bottom of 2 facing pages showing how flanking works.

So no, it is not a houserule. It's in the DMG as an option. Just like multiclassing and feats are options in the PHB. 

Quote from BioWizard >>

Flanking is an optional rule, pg. 251 of the DMG. Quote, "If you regularly use miniatures, flanking gives combatants a simple way to gain advantage on attack rolls against a common enemy." There are then six (6) pictures at the bottom of 2 facing pages showing how flanking works.

So no, it is not a houserule. It's in the DMG as an option. Just like multiclassing and feats are options in the PHB. 

 .....

what if you don’t regularly use miniatures. Then does it no longer apply to anything? 

It’s not a “standard rule” but is an “optional rule”.

as an optional rule, it still has raw and rai. Lol. This is one of those moments to argue just to argue so I could go to PM and discuss how it’s raw an optional rule only for in-person games which EXPLICITLY use miniatures. (Online uses tokens. Which raw is not a miniature).

but that’s a waste of anything but a fun thought experiment argument.

point being. Flanking is a bad example in this context, cause being an “optional rule” is not much different than being a “house rule”.

My on topic argument would be:

”well, if you allow flanking which isn’t a standard rule, why not allow my char extra knowledge or languages, they could optionally learn that later anyways...”

see the slippery slope flanking as an example can bring up?

🤷🏼‍♂️
In debates of Raw vs rai For mechanics and such that can be gamebreaking, or generally throw off the entire balance of encounters and story and etc. I tend to only stick to standard rules interpretations, and not use Homebrew or optional rules.

Ask your dm and make it only on one thing like rangers favored enemy

In debates of Raw vs rai For mechanics and such that can be gamebreaking, or generally throw off the entire balance of encounters and story and etc. I tend to only stick to standard rules interpretations, and not use Homebrew or optional rules.

All of which from your original post is completely irrelevant to my first point, which was that advantage is usually conferred conditionally, and thus temporarily, and is not permanent. Just like your character can't (under the OPTIONAL rule) permanently get advantage to attacks just because he flanked a guy once, your character also shouldn't permanently get advantage to all history checks because he read some books once. He might get advantage in recalling information from the books he read, but not from books he never read, and surely there are thousands of those.

So you ignored my point, which was that advantage is temporarily and conditionally determined in most cases, and decided to argue about the merits and demerits of the (optional, published-in-the-core-books) rule I cited as an example. The example is just an illustration of how advantages occur based on temporary conditions, not permanent bonuses to a character forever.