Most occurrences are on non-Japanese prints of cards where the card's name was established before the archetype was; the most common usages are on old "Archfiend" cards such as "Summoned Skull" and "Axe of Despair" for which the name is well-established and it would not be appropriate to rename the card.
On non-Japanese cards, archetype conditions are listed in parentheses at the start of the card text (but after Materials) on a separate line from the rest of the card text for all cards except non-Effect Monsters, on which they are listed at the bottom of the card description box. On Japanese cards, archetype conditions are listed at the start of the card text, but still as part of the main body and not in parentheses.
Because an archetype condition is not an effect, it is unaffected by cards such as "Skill Drain". It is also the only text to be printed in the primary card text of a Normal Monster that can affect gameplay in any way.
Archetype membership is determined by a card's name: an archetype's support (and anti-support) cards list a specific string in their effect, and a given card is a member of that archetype if its name includes that string. Because Yu-Gi-Oh! is originally a Japanese franchise, most such support is determined by Japanese effects and names, and when cards are localized for non-Japanese regions, a suitable translation is chosen to name the archetype and be used in the names of all of that archetype's members and the effects of its support cards, and no other cards ever use that string in their names.
There are two cases where this system may break down: where the first support cards are released much later than the first members, and those members were localized without the archetype's string in their names (sometimes including anime localizations); and where previously-localized nonmembers were given names that contain the archetype's string. In both cases, there are two possible solutions: rename the card, or specify its membership status; both ways have been used in the past. For example: the English card text of "Arsenal Summoner" specifies that "Celtic Guardian", "Winged Dragon, Guardian of the Fortress #1", "Winged Dragon, Guardian of the Fortress #2", "Guardian of the Labyrinth" and "The Reliable Guardian" are not "Guardian" cards; and "Oscillo Hero #2" had its English name changed to "Wattkid" to include it in the "Watt" archetype. Archetype conditions are just a formalized type of the first method, used where a card cannot be renamed because its current name is well-established and well-known by fans and players, as is the case for "Summoned Skull" and "Axe of Despair".
The condition is formatted as:
- (This card is always treated as a(n) "[archetype]" card.)
or if there is only support for monsters of that archetype:
- (This card is always treated as a(n) "[archetype]" monster.)
On Japanese cards, the condition is formatted as:
This type of condition was first seen in Absolute Powerforce on "Chimera the Flying Mythical Beast". While "Archfiend" cards without "Archfiend" in their name had long been listed on the official website and in rulebooks, the condition text was not added to them until Battle Pack 2: War of the Giants.
So far, archetype conditions have only been used to include cards in the "Phantom Beast", "Archfiend", "Utopia", "Noble Arms", "Elemental HERO" and "Superheavy Samurai" archetypes. As there is only support for "Phantom Beast" monsters rather than "Phantom Beast" cards, the archetype condition used on "Chimera the Flying Mythical Beast" only includes it as a "Phantom Beast" monster, whereas other cards with archetype conditions are included as cards of that archetype.