"Cloudian - Smoke Ball" (above) and "Cloudian - Turbulence" in the artwork of the latter card.
"Cloudians" require an advanced degree of skill to use properly, because their usefulness depends on how many Fog Counters there are on the field. Most "Cloudians" cannot be destroyed by battle, but their low ATK leaves their controller open to taking damage unless "Spirit Barrier" or "The Sanctuary in the Sky" are used. Once your support cards are in play, the opponent will find it frustratingly difficult to get past a "Cloudian" Deck's defenses. While the opponent is being stalled, the "Cloudian" user can then generate enough Fog Counters to whittle down the opponent's defenses, eventually leaving them with nothing to protect themselves from the otherwise "weak" monsters.
A "Cloudian" Deck can focus on swarming the field, on destroying the opponent's cards, on inflicting effect damage with "Natural Disaster", on a Stall Victory, on raw Beatdown power with "Cloudian - Nimbusman", or any combination of the above. "Cloudian - Eye of the Typhoon" can also provide some field control by messing with the battle positions of opposing monsters. The seemingly weak monsters in the Deck such as "Cloudian - Altus", "Cloudian - Cirrostratus" and "Cloudian - Acid Cloud" become surprisingly useful with enough Fog Counters on the field. Through cards like "Cloudian Squall" and "Fog Control", anyone facing these three puff-balls will quickly find themselves with no monsters, no back row, no hand and no options. Hence the name: "Cloud Control". A killer combo can be made by using "Cloudian Squall" to put a Fog Counter on "Cloudian Turbulence" every turn. Then you can play a "Cloudian Smoke Ball" and tribute it to play "Mecha Sea Dragon Plesion", and every turn tribute the "Smoke Ball" that you can play each turn to devastate your opponent's field.
Also, since most "Cloudians" are Fairy-Type, a good card to add is "Athena", who can use her effect to Special Summon powerful "Cloudians" from the Graveyard by sacrificing smaller "Cloudians" like "Cloudian - Smoke Ball". While the Special Summoning is generally a good idea, bear in mind that most "Cloudians" gain their Fog Counters when they are Normal Summoned.
The effects of the "Cloudians" work when they have enough Fog Counters to pay for them. The number of Fog Counters they get depends on the number of "Cloudians" on the field when each "Cloudian" is Normal Summoned. Since they have many cards to quickly Summon Cloudians like "Cloudian - Sheep Cloud" and "Cloudian - Turbulence", they can quickly swarm the field. The strength of the "Cloudians" lies in their ability to destroy cards using the Fog Counters, limiting the opponent's ability to respond.
These are the main power source for "Cloudian" monsters. These counters should be placed mainly on the "Cloudian"-player's monsters but certain "Cloudian" cards can take advantage of Fog Counters anywhere on the field (e.g. "Cloudian - Nimbusman", "Diamond-Dust Cyclone").
"Cloudians" generally gain Fog Counters when they are Normal Summoned. Since Fog Counters can only be placed on face-up monsters, "Light of Intervention" is a good card to use in a "Cloudian" Deck. A good way to gradually strengthen your monsters is to have "Cloudian Squall" out and stalling tools to buy turns for accumulating Fog Counters.
"Cloudian" Decks are often underestimated because, while most of the "Cloudians" cannot be destroyed by battle while in Attack Position, if they are in Defense Position they are destroyed by their own effects.
It wouldn't hurt to add a "Gozen Match" or "Rivalry of Warlords" in the Side Deck as nearly all the monsters are one Type and most of them are one Attribute. If you know what type of Deck your opponent uses, you could slip in one (or both) of the above cards to limit your opponent's Summoning abilities while leaving yours almost untouched.
Another helpful card in a "Cloudian" Deck is "Mira the Star-Bearer". Its effect protects your "Cloudian" monsters from being destroyed, and it's fairly simple to summon with "Cloudian - Turbulence". If you choose to play "Athena" then a good card to use is "Valhalla, Hall of the Fallen"
While "Cloudians" cannot be destroyed by battle while in Attack Position, cards like "Stumbling", "No Entry!!", "Earthquake", "Spider Web" and "Karakuri Shogun mdl 00 "Burei"" would cripple this Deck as the these cards all force monsters into Defense Position making the "Cloudians" destroy themselves. "Spiders" are also a threat for the same reason, since many of them change the Battle Positions of a monster to Defense Position.
Effect-negation cards, like "Skill Drain" and "Angel O7," can make every "Cloudian" except "Eye of the Typhoon" über-fragile on the field. Without their effects or a significant offensive boost, all of the "Cloudians" save "Typhoon" are easily picked off by monsters with >1800 ATK and many of them in this day and age can be easily Normal or Special Summoned. Their low ATK can also make them easy fodder for the "LV" "Armed Dragons", "King Tiger Wanghu" and "Deck Destruction Virus".
"Savage Colosseum" combined with anti-attacking effects also gives trouble, because any "Cloudian" will be destroyed by a card's effect instead of by battle if any don't attack; this can also be combined with "Begone, Knave!" and "Des Counterblow" to not only remove them from the Field but also bump off Fog Counters (this is especially an issue with "Nimbusman".) Speaking of Fog Counters, the archetype's main offensive cards ("Nimbusman", "Cirrostratus", "Altus", "Acid Cloud" and "Diamond Dust Cyclone") all rely on a steady supply of Counters to use their effects, making most "Cloudian" decks weak against "Exhausting Spell" and "Counter Cleaner."