Player deaths are always nasty and annoying. If you want to protect yourself against that other than by getting resurrected by a companion, such as a cleric with Revivify or stronger resurrection spells, how would you go about that?
I'm aware of the Clone spell, but that's an 8th-level wizard-exclusive spell (although it can be cast on other creatures, so it's still an option for non-wizards if there's one in the party).
The only other feature I'm aware of is the Unearthed Arcana Mystic's level 20 feature which gives you a 55% chance to automatically revive 1d3 days after your death.
What possibilities exist for members of other classes (potentially using magic items)?
I'm primarily interested in features to survive actual death, not zero-HP-unconsciousness. Feel free to include anything that helps against zero-HP-situations, but it's not quite what I'm looking for.
Best Answer
My answer will be based on Spells. I can't remember any magic item that works like what you want (except for casting these spells).
Official Ways
Contingency
Contingency from a Wizard multi-classed into a class that can cast resurrection spells, e.g. Wiz 11/Cleric 9. Not optimal, but official. Note that Contingency only states
not "A Wizard spell".
If you have access to a Contingency spell scroll, you can read it if you have at least 1 level in Wizard. Note that you can only cast a spell from a scroll
The use is simple: Trigger is "me dying", spell is Revivify. Other res spells have cast time of 1 hour, not 1 action (Raise Dead, Reincarnate, Resurrection and True Resurrection at least - can't remember any other).
Death Ward
Straight-forward
Not exactly being resurrected but stopping death, which is essentially the same.
Wish
Well, Wish can do anything as long as you word it correctly and your DM allows it. "I wish that next time I die, I get instantly resurrected". (Or resurrected after 1 week, or anything else you... Wish.)
Anything that grants you a cast of any of the earlier spells
Welp, obvious one as well. In particular, Gate into Efreeti into Wish. Candle of Invocation works as well, but your DM will not be giving one to you.
Depending on your definition of "others"...
You could also have creatures conjured (or enslaved?) for you that can cast resurrection for you. True Polymorph gives you a friendly creature (from a rock). PixelMaster has mentioned War Priest, from Volo's Guide to Monsters, who is CR9 and can cast Revivify - there you go. Find a large rock, cast True Polymorph, create a War Priest.
Glyph of Warding - slightly modified
Since this errata, Glyph of Warding can also be used for that purpose. Originally it said
but it has changed to "When you cast this spell, you inscribe a glyph that later unleashes a magical effect."
and
As per V2Blast's comment, if you define the trigger as being "It triggers when I die", you are the one triggering the effect, thus you're the target. You could then cast Revivify and put the Glyph somewhere.
It's not a Homunculus/free resurrection due to this limitation (clarified in the same errata):
So you can't just cast it in an object and walk with your free resurrection inside the dungeon.
This would be best used in your own house or something like that for not being assassinated.
I've had an (evil tyrant and paranoid) NPC doing that, glyphing his own bed. Just in case someone would kill him during his sleep. It's essentially a (greatly) nerfed Contingency that can be used by other (than Wizard) classes.