The art isn't the greatest out there, and the update schedule makes "erratic" look like an understatement, but (most of the time) the story makes up for it. Although he has been doing better lately. See Schedule Slip below.As can be inferred from the title, it's based on the D&D Campaign Setting Planescape, and homages The Hitchhiker's Guide to the Galaxy.
Art Evolution: The art may not be the best in the world, but the latest strips are an extreme improvement from the first few chapters. ESPECIALLY the Talking Heads strips. It's visibly obvious that Swift has improved over the duration.
Artifact of Doom: The three sacred items of Aoskar. They can survive being pulled into the Nothing, which can unmake planes.
Cross Player: There are three people in the original Sigil party - Torin, Elera, and Talanard. In the Breaking the Fourth Wall strips that show the players behind the story, there are four male characters around the table, one obviously being the DM. Whoever is playing Elera dings the trope meter, take a shot.
Demonic Possession: Railah, a former battle priestess of Cyric, is possessed by the dark god of Fate Jergal as his pawn and puppet in his scheme to unmake the Multiverse.
Earth-that-Was: The Firstworld is quite obviously our Earth, with the alternate trope that it has been abandoned by magic and the Gods rather than reduced to uninhabitability. It's VERY difficult to reach, but Jerak has managed... and fell in love immediately with sunglasses and automatic weapons.
Eldritch Abomination: One appears when a portal to The Far Plane is opened in Dolrak the Arcanoloth's castle.
Evil Laugh: Glowy red rocks don't have to breathe.
Evil Sorcerer: Merrel and the Black Robes are an entire cult of them. Also Delia and the Duergar mage whose name I cannot recall.
Heel Face Turn: Talanard was a Black Robe at some point in the past. (Maybe it would be Mook Face Turn as well, given the one-shot life expectancy of Black Robes...)
Horny Devils: The Succubi in Jerak's caravan are pretty standard, save Winnie. And Milny, even in her pseudo-Succubus shapechange, is too busy being Milny to even try being seductive.
Indy Ploy: Starts with Telv and Tommy 5, and spreads like the plague from there.
DOM: So we need a strategy.
Telv: BORING! Want to do something stupid with me?
Tommy 5: You know it!
Inexplicably Identical Individuals: The Tommys. Same look, same mentality, same Full Plate And Long Sword... same tendency to be the first and only to die. Though that may not be their real names, just the one that Gerand and Telv label them as soon as they meet.
Knight Templar: The Harmonium Guard and the Mercykillers are the traditional Planescape examples, amusingly parodied when a NON-Knight Templar Harmonium - Larry the Tiefling Paladin - is arrested and hung upside-down from the wall for suggesting that Tchick might not be responsible for the destruction of the city block where he was found unconscious.
Noble Demon: Jerak, Grull, and Winnie don't convince much of anyone that they're merchandising for the Forces of Darkness.
No Such Thing As Wizard Jesus: Averted. Aoskar/the Eldest predicted his future destruction and hid a portion of his essence on the Firstworld two thousand years prior, and despite killing that Aspect out of fear and being without deities since the people of the Firstworld still revere him... making Aoskar equivalent to God and Jesus his Avatar.
Noodle Incident: Telv's bio mentions him being expelled from minstrel school for "a strange occurrence know only as "the plague of playing cards." Few had ever used a cantrip spell to such devastating effect."
One of Us: At least enough to know that his webcomic has a TV Tropes page, and to comment on it in his page notes.
Our Dragons Are Different: Fred is an Orange Dragon - not the kind you'd find in an expansion book or 3rd party package, but rather the crossbreed of a male Red and a female Gold.
Our Dwarves Are All the Same: Appears to be Subverted at first - the Duergar (Dark Dwarves) worship Jergal, ex-God of Death and Fate and master of The Nothing, rather than their normal Faerun racial deities. Once you get past that, though, there's not much different about them: they still guzzle alcohol like water and live for a good scuffle (even the mage).
I should point out, though, that Sarn isn't Scottish. (Thanks to his eyepatch, he's forced to talk more like a pirate.)
Our Elves Are Better: Mostly averted - the elves and half-elves are pretty typical to D&D standards - but played straight with Meleras, the Affably Evil Drow Ranger who still worships Lloth but is also willing to work with other races. The fate of the Multiverse at the mouth of The Nothing is that bad.
Schedule Slip: The most common comment in the chatbox on the front page: "It's been (random time amount, usually two weeks to a month)... Where's the next comic?"
He has improved his schedule-keeping skills lately, much to the delight of his fans. It's not perfect, as he notes in one of his footnotes, saying "I kind of feel silly apologizing for one day late, though... since I'm much more accustomed to being a month overdue". But hey.
Welcome to the Real World: Chapter 4 has revealed that the Firstworld doesn't just have no magic and greater technology, it also has discontinued D&D campaign settings that plainly depict Planescape. Some of the characters believe the solution to defeating the unstoppable villains may be inside.
Why Did It Have to Be Snakes?: Talanard is terrified of the Blood River. Thanks to Laser-Guided Amnesia, he doesn't know why, but he is. It's because he used to be one of the baddies, but was killed in one of the blood rivers by another bad guy.