The artworks of "Graydle Impact" and "Graydle Parasite" suggest that the original monsters are liquid metallic alien slime creatures that arrived on Earth and parasitically possess other creatures. Furthermore, it seems that they can mold themselves, such as splitting in two as shown in "Graydle Split" or merging together to form chimera-like monsters, such as the Synchro Monster "Graydle Dragon".
The color scheme of the possessed creatures is based in the three main types of cards: Monster ("Graydle Eagle"), Trap ("Graydle Cobra") and Spell ("Graydle Alligator"). Furthermore, all of the Main Deck monsters' ATK and DEF sums 2000, so far.
Although the specific origins of the name "Graydle" aren't clear, it is a portmanteau of the words "Gray" and "Cradle". "Gray" or "Grays" is a term that is used to refer to a stereotypical small grey alien man.
Fitting the archetype's "parasite" theme, the "possessed" "Graydle" monsters consist of equipping themselves to opponent monsters when destroyed by battle or by specific effects and taking control of them. The support cards so far either aid on using those effects, such as "Graydle Parasite" and "Graydle Impact", or help swarming "Graydle" monsters, such as "Graydle Split".
Other combos include Special Summoning "Graydle Cobra" with "Call of the Haunted" and using "Magic Planter" to draw 2 and then take control of an opponent's monster, then using "Release Restraint Wave" to destroy all of your opponent's Set Spells and Traps.
Their boss monster, "Graydle Dragon" destroys cards your opponent controls up to the number of WATER monsters used for its Synchro Summon; also, if it ends up being destroyed, you can revive another "Graydle" monster to either take control of an opponent's monster or to use it to Special Summon "Graydle Slime" and Synchro Summon another "Graydle Dragon".
- Due to their heavy emphasis on taking control of other monsters, "Graydle" Decks tend to have trouble with cards that prevent control switching, such as "Owner's Seal" and "Remove Brainwashing".
- The "Graydle" monsters' controlling effects target, so effects that prevent targeting will stop them dead. Alternately, "Interdimensional Matter Transporter" and other self-removal effects can help prevent your monsters from being controlled (especially useful if you have ways of bringing them back afterwards).
- Most "Graydle" strategies rely on their cards being sent to the Graveyard for their effects to activate, so Banish effects can quickly shut them down.
- Cards like "Disappear" or "Dark Smog" are useful against the Special Summoning effects of "Graydle Slime" or "Graydle Dragon", as you can wait for their user to declare a target before Banishing it.
- Monsters who can banish opposing monsters that they destroy by battle (such as "Lesser Fiend") can dispose of "Graydle" monsters without triggering their effects.
- The main three "Graydle" monsters ("Eagle", "Cobra", and "Alligator") can only activate their effects if they are destroyed in certain ways; "Eagle" activates by Monster effects, "Cobra" activates on Traps, "Alligator" activates on Spells, and all three will activate if they're destroyed by battle. Consequently, you can prevent them from equipping themselves to your monsters by destroying each with card effects that won't trigger their effects, such as using "Trap Hole" on "Graydle Eagle", "Fissure" on "Graydle Cobra", or "Kozmo Dark Destroyer's" destruction effect on "Graydle Alligator".
- The "Graydle" archetype has a strong emphasis on Continuous Spell and Trap Cards to make their plays, so Spell/Trap destruction can cripple their speed and deprive them of easy ways to trigger the effect of "Alligator" and/or "Cobra". If you don't mind destroying your own monsters, you can also use destruction effects on "Graydle" monsters that equip themselves to your monsters via their own effects.
- "Graydle" monsters are all WATER-Attribute and Aqua-Type, so strategies can be made to counter their Attribute or Type specifically.
- Most "Graydle" monsters (with the exception of "Graydle Dragon") have low ATK and DEF, with none of their Main Deck members exceeding 1500 ATK ("Graydle Eagle") and 2000 DEF ("Graydle Slime" and "Graydle Slime Jr."). Additionally, their strategies often lend themselves to attacking stronger monsters in order to destroy themselves and activate their effects, which means that their user can end up depleting a significant amount of their own Life Points.
- This archetype may be based of John Carpenter's 1982 film, The Thing.
- This archetype has similarities to the earlier "Alien" archetype; the members of both archetypes are extraterrestrial monsters whose strategies revolve around manipulating the opponent's monsters (although "Alien" Decks do so via "A-Counters", whereas "Graydle" Decks use their own monsters' effects instead).