Equipment items with the designation ST are part of a special themed set, and when all items of the set are equipped together your character will transform into a larger sprite. There are currently a total of 13 special themed sets that transform one’s character into a 16x16 sprite when fully equipped. Unlike regular untiered (UT) items, ST items can be purchased for Realm Gold through Mystery Boxes, in addition to having a rare chance to drop from enemies.
All special themed sets, except for the Oryx Awesome Set, confer an additional stat bonus if all four items of the set are equipped together.
Some UT items are part of a set through similar aesthetics, such as the Coral Huntress or Void Archer sets. However, these sets are not considered ST because they do not transform the player to a larger sprite even if the full set if equipped. Like other UTs, these cannot be purchased for Realm Gold.
As of Build X.28.0.5, Archer and Ninja are the only two classes that lack a special themed set that transforms them into a 16x16 sprite.
Themed on: Oryx the Mad God
Set Bonus: N/A
Themed on: Swoll Fairy
Set Bonus: +50 HP, +50 MP, +2 ATT, +2 DEF, +5 SPD
Themed on: Geb
Set Bonus: +50 HP, +50 MP, +8 ATT, +5 SPD
Themed on: Ghost of Skuld
Set Bonus: +80 HP, +30 MP, +5 ATT, +6 SPD, +1 DEX
Themed on: Twilight Archmage
Set Bonus: +40 HP, +15 MP, +2 ATT, +5 DEF, +2 SPD, +2 DEX
Themed on: Phylactery Bearer
Set Bonus: +35 HP, +40 MP, +5 ATT, +10 DEF, +2 SPD, +1 DEX, +5 WIS
Themed on: Unknown
Set Bonus: +75 HP, +5 ATT, +10 DEF, +10 SPD, +5 DEX
Themed on: Unknown
Set Bonus: +7 ATT, +2 DEF, +8 SPD, +11 DEX
Themed on: Tormented Golem
Set Bonus: +40 HP, +10 ATK, +3 DEF, +5 DEX, +15 VIT
Themed on: Unknown
Set Bonus: +25 HP, +30 MP, +7 ATT, +4 DEF, +5 DEX, +6 VIT
Themed on: Horrific Creation
Set Bonus: +3 ATT, +15 DEF, +6 SPD
Themed on: Flesh Collector
Set Bonus: +50 HP, +100 MP, +7 ATT, +6 VIT
Themed on: Unknown
Set Bonus: +115 HP, +3 ATT, +10 DEF, +4 SPD