When the game of tarot was invented, the trump suit was added to the ordinary Italian playing cards to create a kind of superpack of cards that could be used for the game. The motifs represented by the cards of the trump suit were chosen to form a sequence of great significance, an allegorical, philosophical, religious sequence about the way we live our lives — and therein lies much of the fascination with these cards.
In order to design and draw an interpretation of each of the trump cards, it was important for me to understand the sequence of the trumps as best I could. This was especially important when I was drawing one of the trump cards in a way that is somehow different from the typical traditional way or ways that a card may be drawn.
So I read a lot, and I arrived at an understanding that I based my cards on. What I have made in the Rare Triumphs is not a recreation of any particular historical tarot, but rather an interpretation, reached by delving and searching around the earliest days of tarot, watching the way different early tarot traditions developed, and thinking about other possibilities.
So the sequence of the cards in terms of how I have understood and interpreted it for the Rare Triumphs is outlined below. I hope you can see the relationship with more typical tarot cards of the traditional style.
The trump cards can basically be thought of in three sets. The lowest, the middle, and the high.
0-5: These cards represent the earthly domain.
In some tarot traditions, some or all of the popes and emperors that often occupy these positions are substituted out. For a set of four equivalent popes. Or for four equivalent moors. Or for Jupiter and Juno. Or for Bacchus and the Spanish captain. And I have made such a substitution. So in the Rare Triumphs deck these cards represent the conditions of man on earth, as may be seen in the Mantegna series (so-called). The teacher, merchant, nobleman, and president represent some kind of heirarchy of authority figures. While the lowest two, the fool and the worker, form a separate lowly subgroup.
6-14: These represent allegories of what we might encounter in life.
The three virtues are a subgroup unto themselves. The positions of these virtues within the Marseilles sequence are unfathomable to me, but I did not presume to alter these positions. (As mentioned above, the positions of these three cards within the trump sequence as a whole vary a great deal between different historical tarot traditions.)
If we consider the rest of the middle group without these virtues, we begin with quite upbeat allegories (love and victory, represented by a chariot), followed by influences that may change things for better or worse (fortune and time), and leading ultimately to downfall and death.
I have to be honest, I think that is a relatively clear sequence, if a not particularly optimistic one.
15-21: Here we enter the more cosmological realm.
In the beginning there is only darkness or the absence of light (chaos). This is then followed by a series of increasingly bright lights in the sky: lightning, stars, the moon, and the sun.
The final two trumps again form a kind of subgroup, and things become a little more abstract. And what is brighter than the sun? a riddler may ask. And the answer may come: The Truth is brighter than the sun. Or The Glory of the Lord. Or something like that.
Well, Fame (or renown) is the judgement of our peers and our audience. The fame of great deeds can live on after death. Fame arrives as a herald bringing the news. Fame flies.
And the highest card is eternity because that is the biggest and most unfathomable thing of all.
 Usually always represented by a man hanging upside-down, a shame painting as punishment for a traitor.  Usually always represented by the devil.  Maybe I should mention that this card, sometimes called the trumpet or the angel, and sometimes the highest card, may be called fame or renown in Minchiate, though this is not the only appearance of fame in historical tarot. Several of the other "less common" names I have used are also rooted in historical usage, I am only mentioning this instance explicitly as perhaps it is a bit less well-known. Or maybe it is actually just as well-known, I don't know. Perhaps I should say as well that in general in naming the cards I have tended to name them after the idea that is represented in the drawing, rather than a literal description of what's in the picture as sometimes happens.
You can order the Rare Triumphs tarot cards here.