Planes Walker
This is the plane of most adventures and is certainly almost always the default.
Prime Material Plane
This iconic 3rd level spell is often considered overpowered for its level but even the game designers think that that's perfectly fine
Fireball
If you are ever ganged up on and need to get away without risking a hit, the Disengage action is a guaranteed way to be safe while you exit.
The Sentinel feat allows opportunity attacks regardless of disengage
This city in my current campaign shares a name with a city from the Gears of War series.
Montevado
This legendary deck of cards is usually found with only 13 cards but can sometimes be 22 cards instead.
Deck of Many Things
Anything can be a weapon if you're holding it right. However this weapon does not deal any damage and has a maximum thrown range of 15 feet.
Net
One could describe this oppressively grim plane as "tim burton without whimsy"
Shadowfell
In the 2014 rules, this nearly useless spell had a concentration time of only 1 round
True Strike
Are you camping in the wilderness and need someone to take watch at night? Just tell someone with dark vision to do it since they can see unimpeded at night.
Darkvision only turns darkness into dim light, still giving disadvantage on perception based on sight
When the party met Lorelai at The Slumberyard, this made her dress stand out from your typical dress.
It has pockets
This November I will have been running d&d for this many years.
10
In 5e casting True Seeing on a creature allows them to see 120 feet into this plane
Ethereal
In the event that you are low on HP, would really like to use your reaction to stand up, as well as Charmed, Frightened, Paralyzed, Poisoned, and Stunned, you'll wish a bard or cleric had cast this spell on you.
Power Word Heal
A common rule ignored is that weapons with the Heavy property give disadvantage if the wielder isn't strong enough.
Heavy gives Small creatures disadvantage, it isn't strength based
The summer season I'm my campaign setting is called this.
Coldhearth
Most people know a Bag of Holding has a weight capacity of 500 pounds but many forget that this is its volume capacity
64ft³
Many spells or items allow a creature to either create or use this type of lesser plane
Demiplane
In need of an escape? Well I hope you brought a forked metal rod worth at least 250 gold attuned to your destination, otherwise you won't be casting this spell.
Plane Shift
The player's handbook has a list of equipment, tools, and other adventuring gear. Prices vary but the most budget friendly adventures need not worry as the most expensive thing on the list is only 100 gold pieces
The spyglass costs 1000gp
Booker Lindrow, the bbeg from my previous campaign, developed this homebrew spell that would permanently severe a person's connection to the Weave.
Arcane Rot
The spell Detect Thoughts has this as it's witty material component
1 copper piece
Creatures in this plane need not eat nor drink and they also do not do age
Astral Sea
Whether you want it or not, if your character has been circumcised, this spell will undo that. This spell also does not require you to be dead first.
Regenerate.
A Shambling Mound is a large Plant type creature. The best way to kill it isn't just fire but especially lightning. {2 part answer, must have both}
It is resistant to fire damage and lightning actually heals it instead
What year is it?
6001
Beholders do not mate and almost never mean to reproduce, despite that beholders are known to do this that results in a new beholder being created nearby
Dream about another beholder, warping reality and making a new one appear