For reference, let's start with unpacking the blinded condition in D&D 5e:
- A blinded creature can't see and automatically fails any ability check that requires sight.
- Attack rolls against the creature have advantage, and the creature's attack rolls have disadvantage.
The first clause that states you can't see is kind of obvious but the second part of that sentence is important, you automatically fail checks that require sight. This seems crippling, however if you play your character creatively you can bypass it by proving to your DM that the checks do not necessarily require sight.
For example: When your party makes perception rolls to spot an orc perhaps you can hear the sound of their breathing, smell their perspiration, or even feel the vibration of their footsteps across the dungeon floor. Or If you are trying to detect a trap you can feel across the floor to find it but make a Dexterity check to avoid triggering it, use a ten foot pole, it is your best friend, or perhaps you hear the tripwire in the wind, or smell the lubricant on the metal on the hinges of a mechanism.
I would recommend gaining expertise in, or at the very least being proficient in, Perception and Investigation at some point through feats or multiclassing or being a rogue or bard and having a decent Int or Wisdom - along with potentially getting a good Dexterity, as you will have to make a lot of Sleight of Hand and Acrobatics checks to prevent triggering traps or falling off of edges. It is recommended that you expertise those skills so that you can be able to more consistently pass the skill checks your DM will throw at you when you attempt to justify smelling the boot polish of an enemy soldier and whatnot.
The second clause however is the crippling part, the creature gets advantage to attack you and your attacks have disadvantage.
If your DM is willing to allow UA content, you can take a level in fighter, ranger, or paladin and take the Blind Fighting fighting style (from UA: Class Feature Variants):
Being unable to see a creature doesn’t impose disadvantage on your attack rolls against it, provided the creature isn’t hidden from you.
Or if you are not one of those classes that has a fighting style you can take the Fighting initiate feat (also UA) to get that fighter fighting style as well.
This would solve the problem of you missing 25% of all melee attacks because it would allow you to roll them like a regular character.
However, to deal with the second part of that clause (that all characters have advantage to hit you): as @gates-vp's answer and @V2Blast's comment on it mentioned, the Alert feat (PHB, p. 165) is also a great option as it removes that disadvantage and allows you to potentially survive a bit better. The description of the Alert feat says:
- You gain a +5 bonus to initiative.
- You can’t be surprised while you are conscious.
- Other creatures don’t gain advantage on attack rolls against you as a result of being unseen by you.
(The third bullet point was updated in errata; it originally read "as a result of being hidden from you.")
However, if your DM does not allow UA materials and is not allowing feats, try to ask for blindsense or perhaps a bit of tremorsense as mentioned in other answers.
However I would not recommend blindsense or tremor sense as it could potentially allow you to see through walls and such, that is why if I ever was to dm such as character I would limit the blindsense or tremorsense to 5-10ft in order to limit that craziness.
It also does allow you to bypass or outright ignore most forms of illusion magic and certain frightening abilities which some dms might be wary of.
Tremorsense might be a better option than blindsense as blindsense is sight using other senses to a specific radius which is all well and good, but I feel it removes the disadvantages of bindness too much.
Tremorsense on the otherhand is a really nice ability as it is like blindsense, but it lets you feel the vibrations of the surface you are on which applies some limitations, you can't see if you are flying or jumping as you must be grounded to use it.
If none of the above options work, I would recommend that for martial characters, you look at the following class options:
Being a Barbarian and using Reckless Attack every turn to negate the disadvantage; the advantage to hit you is already there anyway so you don't have to worry about it, as in the PHB it states that no matter how many sources of disadvantage you have, they don't stack, and a single source of advantage negates them all.
A samurai fighter would allow you to gain advantage a limited number of times per rest to negate your disadvantage to hit and extra hp to stay up and kicking under many blows.
The Inquisitive rogue allows you to gain advantage on Perception and Investigation checks when moving at half speed at 9th level, allowing you to easily spot things. And being a rogue in general allows you to eventually get blindsense and such.
The ranger class in general particularly the UA revised version would allow for you to grab the blinding fighting style and eventually get blindsight, though it is up to dm ruling whether or not the seeing of invisibility applies.
However, if you are a full caster, half-caster, or even a one-third caster, you can look at the following options:
Grab the find familiar spell, allowing you to see through the eyes of your familiar. The beast sense spell would allow you to see through the eyes of a loyal pet and companion (a good reason to go Beast Master ranger).
Use buff spells such as blur, sanctuary, mirror image, blink, shield, invisibility, and such to negate the advantage to hit against you.
Use spells such as darkvision and true seeing to potentially grant you temporary sight.
Get divination spells to be able to see things that others cannot (i.e. detection spells such as detect magic and such to allow you to perceive certain things).
Get magic missile so you only have to locate the create to decimate them. Or spells that require saving throws such as vicious mockery, hold person, fireball, toll the dead, etc. so that you only have to locate the create to do damage.
Use faerie fire to get tasty advantage.
Use spells such as darkness to obscure yourself; you are blind anyway, so being shrouded in darkness and next to impossible to hit is nice.
Focus on spells and cantrips that use an area of effect, such as thunderwave, destructive wave, or thunderclap, so you do not even have to locate the target; you just plaster an AOE in their general direction. However, this could lead to friendly fire if you aren't an evocation wizard or sorcerer.
So without further ado, I present you the last contingency on the list:
- Ignore the blinded condition entirely. If your DM allows it, just say you have learned to live with being blind and it doesn't affect you mechanically at all. However, I do not recommend this option as it does not let you be creative whatsoever in playing your character to bypass these limitations.
Have fun adventuring, I wish you luck in creating a blind ninja!