Compendium of all the "Official" Familiars

Quote from SunIsGettingRealLow96589 >>

I thought you could adopt any living cr0 creature as your familiar, and you get telepathy and can see through its senses, but it isnt summoned, and if it dies, its dead.

I understood the gazer to be one of those.

Its an actual living creature, and you might be able to make it a familiar, but it cant be summoned and instead you have to heal it to keep it alive.

Maybe ive been playing it wrong all these years

That is not how Find Familiar has ever worked in 5e or 5.5e. If you read the description of the Find Familiar spell, you'll see how it works according to the official rules. (Obviously many people may have house rules about this and whatever works for you at your table is fine.)

What you are describing is much more along the lines of how the Beast Master Ranger's animal companion worked in 5e, though even that was still limited to Beasts, so a Gazer wouldn't qualify for that either.

Well, i know thats not right: from DragonHeist, Xanathars Lair, room x13:

"Albino Gazer. Xanathar dreamed this gazer into existence and sent it to spy on Thorvin, whose loyalty the beholder is beginning to question. The gazer is itself disloyal. A wizard character can befriend it with a successful DC 11 Charisma (Persuasion) check and turn it into their familiar with a find familiar ritual. When the gazer becomes a familiar, its alignment changes to match that of its new master."

In Ghosts of Saltmarsh, on firewatxh island, there is a seagull who was a wizards familiar 10 years ago, has been living on the island ever since, and a player can make them a familiar:

"RESTORING VIRGIL: Any character who can cast find familiar can attempt to restore Virgil to its former role, taking the gull as their own familiar."

Quote from SunIsGettingRealLow96589 >>

Well, i know thats not right: from DragonHeist, Xanathars Lair, room x13:

"Albino Gazer. Xanathar dreamed this gazer into existence and sent it to spy on Thorvin, whose loyalty the beholder is beginning to question. The gazer is itself disloyal. A wizard character can befriend it with a successful DC 11 Charisma (Persuasion) check and turn it into their familiar with a find familiar ritual. When the gazer becomes a familiar, its alignment changes to match that of its new master."

In Ghosts of Saltmarsh, on firewatxh island, there is a seagull who was a wizards familiar 10 years ago, has been living on the island ever since, and a player can make them a familiar:

"RESTORING VIRGIL: Any character who can cast find familiar can attempt to restore Virgil to its former role, taking the gull as their own familiar."

Well, yes, certain published adventures have specific elements that override the general rules. That doesn't change how the general rules work.

Eh. Pretty sure there was something in Dragon Magazine back in the days of first edition that homebrewed it. Virgil was first published in 2004 but that cant have been the first one.

The idea of adopting an animal as a familiar instead of conjuring one from thin air isnt too unreasonable. You got the telepathic communication and seeing through their senses. But we always played it as it remained a real animal, so you couldnt put it in a pocket dimension or resummon it to get it back to.full hp. If it hit zero hp, it went unconscious and you had to heal it to keep it around.

That was how the gazer was balanced, since it could do a couple eye beam attacks per turn. But if it got hit, it was probably unconscious and you had to spend actions and resources to keep it alive 

But if you want a disposable familiar with no heart, i guess stick with the phb rules.