Aged counterpart

Aged counterparts are a group of monsters, which have been aged by "Time Wizard". Each aged counterpart has a card featuring their younger self. The method through which "Time Wizard" ages them varies.

"Thousand Dragon" and "Dark Sage" are the only aged counterports in the OCG/TCG, with "Baby Dragon" and "Dark Magician" as their respective younger counterparts.

Manga
If the effect of "Time Wizard" is successful, all monsters on the field are aged. Typically monsters become visible wrinkled, decayed and rusted, resulting in them being much weaker or destroyed.

"Baby Dragon" is the only monster shown to have been positively affected.

Anime
Aged counterparts functioned in the anime, largely the same as in the manga.

An additional card is shown to benefit from the aging effect of "Time Wizard"; "Dark Magician", which becomes "Dark Sage". Like most monsters, "Dark Sage" is weakened in terms of ATK, but gains effects.

OCG/TCG
The anime and manga aging process did not conform well to the rules of the real world card game.

"Thousand Dragon" was instead made a Fusion Monster, with "Time Wizard" and "Baby Dragon" as its material.

"Dark Sage", which was released much later was given a Summoning method closer to its anime self. It is a card included in the Main Deck, Summoned by Tributing "Dark Magician" after applying the positive effect of "Time Wizard". Unlike its anime self, it is stronger than "Dark Magician" in terms of ATK and DEF, but has a weaker effect.

Yu-Gi-Oh! Forbidden Memories
In Yu-Gi-Oh! Forbidden Memories, all the aged counterparts can be created through Fusion Summon, using "Time Wizard" and the younger counterpart.

If the player does not have the actual card for the aged counterpart, they can Summon the monster through Fusion Summon. If they have the actual card, they can Summon it normally, without performing a Fusion.

Unlike other media, the younger counterpart, can be one of many cards.