Our group just hit 18th level. Here's what you are missing if you never player this high

[BMaC]

Our group has been playing 5th since early 2015. We decided that our latest campaign would have a goal of reaching level 20 through XP leveling. We wanted to see for ourselves what the experience of high level play is for both DMs and players. Let me say this: high level play is hard for the DMs and it is challenging for the players but the rewards are worth it. Just a few things that happened in our game last night:

1. Our wizard cast Antimagic Field and grappled a Lich while the rest of the party dispatched its minions (in a low point the wizard, not realizing the Lich was immune to non-magical piercing damage, also repeatedly stabbed the Lich in the neck with a dagger that had not been taken out of its scabbard since level 2).
2. Our paladin went toe-to-toe with a Pit Fiend in a small village while walls of fire and meteor swarms devastated nearby buildings.
3. Our warlock True Polymorphed into a Planetar to engage in aerial combat with an Ancient Blue Dragon.

High level play requires a bit of homework by the DM and players but I hope that more players will play the game to 20th. Our group doesn't intend to continue with this party after we hit 20 but we'll be glad that we went this high so that we could fight iconic high level monsters and travel to crazy places (Sigil the session before) and see for ourselves how the game stands up at the high end.

 

[Draegn]

We had a dark elf wizard challenge Moradin to one on one personal combat, he almost won. Yet the dwarfs do now fear the day known as Draenen ddu, for, on this dark day the fires of Moradin's forge were almost extinguished causing a deathly chilling fever to take many dwarfs. This day is now spent stoking the forges and hearths through all dwarf lands to ward off any possible return of the fever.

 

[BMaC]

Yeah, everything is turned up to 11! If the group gets into the spirit then it's great fun.

 

[S'mon]

My current 5e PC group:

PCs
1. Claw, Lord of Ravenmoor & Warden of the Storval Stairs - Goliath Barbarian-19
2. Quillax, Lady of Wolf's Ear & Warden of Jorgenfist - Human Druid-19
3. Sandor Sunneson of Mystara, Prince of Soderfjord - Human Barbarian-17
4. Shieldbiter of the Wilderlands - Dragonborn Barbarian-20
5. Drakhaien, Elf Rogue-17

You can read of their thrilling adventures, and a little bit of petty GM-player squabbling, here!

Generally I find that very high level 5e is more grounded than prior editions. The current group have mostly been fighting giants, and are still easy to challenge.

 

[TwoSix]

I'm just starting up a Ravnica game, which is planned to run from 9th all the way to 19th-20th. I've run a PF game from 8-20 before, so I'm excited for what looks to be a much easier time running a high level game.