These complement your Pokémon searchers. Pokémon searchers convert cards in hand to cards on the field; if you play a Holon Mentor along with every card it found, your hand now has 2 fewer cards than before. Play Professor Elm's Training Method and the Evolution it found, -1. You will need other Supporters or Poké-Powers to refill your hand so you don't run out of options.
A great general-purpose card draw Supporter. Steven's Advice is reliant on your opponent having Pokémon in play, but most will, especially if they used Jirachi early-game to setup and it's now chilling on their Bench.
You can expect to draw 3 or more cards off Steven's Advice most of the time. Say your opponent plays Holon Mentor, Lanette's Net Search, or Pokémon Fan Club, and puts two Pokémon onto the Bench; those plus their Active makes three.
Note that the Hidden Legends version is misprinted: the restriction starts at having 7 or more cards in hand, not more than 7.
Played alongside Holon Transceiver as part of the Holon Engine.
They are generally weaker than TV Reporter or Copycat, but their strength comes from being searchable off Holon Transceiver.
Playing δ Pokémon for Holon Adventurer is a bonus, but not a requirement.
A simple draw 3, provided you don't have any Stage 2s. The card says "in play", but you should not play it if you have Stage 2s in your deck, period.
A draw 3 Supporter is actually competitively playable in RS-PK, unlike in later eras.
Draw 3, then discard 1.
Played in decks that benefit from having certain cards in the discard. Holon Supporters can also be played for more discard outlets.
TV Reporter can be better than Mary's Request, even in decks without Stage 2s, as it can discard dead cards as a defense against late-game Rocket's Admins.
This card evens the odds if your opponent has more cards in hand than you.
Often played in decks with Trainer locks. Unplayable Trainers stuck in your opponent's hand strengthen your own Copycat.
Decks that mulligan a lot (because of low Basic Pokémon counts) also benefit from Copycat.
This card greatly rewards you if you are able to dump your hand before using it.
Played in decks with plenty of (non-Supporter) Trainers that can be played with no restrictions in a single turn.
A staple digging engine. A common early-game sequence is to search for Jirachi, retreat to it (Holon Mentor can grab both Jirachi and Holon's Voltorb/Magnemite for this), and immediately use Wishing Star, which doesn't require Energy.
Since Jirachi needs to be Active to use Wishing Star, it's usually only valuable early-game, or after a KO if you also have a switch card or Heal Energy (promote Jirachi, use Wishing Star, then use the switch card or Heal Energy to switch/retreat to your attacker and continue attacking).
Jirachi is usually not meant to attack, but there are times when Metallic Blow can be handy. If you're walled by Latios ex δ's Ice Barrier, Jirachi can come in and threaten a 2HKO with Metallic Blow.
Quick Search is an incredibly powerful Poké-Power. It gets any card from your deck, no restrictions.
Pidgeot's other stats are also decent. It has 0 Retreat Cost, Fighting Resistance, and a 40 damage attack for 2 Energy in Clutch. Don't overlook attacking with Pidgeot; it can be very effective against Fighting-types like Exeggutor δ, or if you're able to Pow! Hand Extension Energy off the opponent's Active, rendering it unable to attack back.
Pidgeot is usually played in Stage 2 decks, where Rare Candy can accelerate to either Pidgeot or the attacking line.
If you have Rare Candy, Pidgeot, and another Stage 2 in hand, don't Rare Candy into the other Stage 2. Rare Candy into Pidgeot, Quick Search for another Rare Candy, then Rare Candy into the other Stage 2.
If you start with Pidgey and attach an Energy T1, then Rare Candy to Pidgeot T2, you have the option of Quick Searching for an Energy to power up Clutch. This might let you donk your opponent, or KO their Dark Dragonair and ruin their setup. If you play Double Rainbow Energy, you can even Clutch for 30 damage on T1 with the right hand.
If your deck is δ-heavy, Holon's Castform can act as a decent draw engine, albeit only early-game, as it costs you your attack for the turn. All those extra cards will make good discard fodder for Holon Supporters.
Like with Dunsparce, starting with Holon's Castform is a consistency issue. Swoop! Teleporter is an option. Otherwise, look to start with δ Pokémon that can have their Retreat Costs reduced to 0: Latios ex, Latias, Pikachu (when it evolves).
Delta Sign is basically a Holon Researcher effect every turn.
Fearow's HP is relatively low. One Special Circuit from Rayquaza ex δ plus a tick from Cursed Stone is enough to KO it.
Note that there is no Spearow δ.
Snappy Move draws a card, then gets rid of Aipom. Specifically, it bottom-decks Aipom, so you can search for it again.
It can be used to "store" a draw before you play Admin or any other Supporter that draws up to a certain hand size.
Aipom's role in increasing deck consistency is turning late-game Basic searchers into draws. In Arcanine ex for example, you have 3 Great Ball, but sometimes you just don't need another Basic on your Bench as it would turn off Houndoom. In that case, Great Ball for Aipom and cash it in for a draw. Another example is in Blastoise ex: you might Holon Mentor for Lugia ex and Holon's Castform to pay for Elemental Blast, which leaves you with 1 more Basic to grab. Why not let that be Aipom if there's no other Basic you need?
Like Aipom, Lapras converts excess Basics from Holon Mentor into other cards:
Professor Elm's Training Method for an Evolution
Rocket's Admin. if you're planning to go off with Extra Energy Bomb next turn
Holon Scientist/Steven's Advice to draw a lot of cards if your opponent's hand/Bench is large
Castaway/Scott to build up card advantage again with a chain of Supporters searching Supporters
Lapras is a really bad starter due to its 2 Retreat Cost, but as a Basic it's unavoidable that you'll start with it sometimes. Have switch cards or Swoop! Teleporter in your deck to recover from these starts.
Energy Draw is a draw engine that doubles as a way to get Energy in the discard.
Surprise! Time Machine is often used to reset Energy Draw.
Smooth Over lets you choose your next draw. Combine it with an immediate draw Supporter/Poké-Power for effectively Quick Search.
You can put Windstorm on top and not draw immediately if you're anticipating Cessation Crystal.
Backup is a Professor Birch effect every turn.
If your deck plays a lot of Trainers that you burn through quickly, Porygon2 is an option for refilling your hand. It's also a good counter to getting Admin-ed to a low hand size.
Sharing gives you information on the opponent's hand and lets you copy one of their Supporters.
Milotic δ is effective against Scott and Castaway, as your opponent cannot play any Supporters that they searched for immediately. It's less effective against the Holon Engine, as it cannot copy Holon Transceiver.
The downside to using Milotic is that Feebas is incredibly fragile — it's tied for the lowest HP among all Basic Pokémon in the format.
Primal Light is an Energy Search every turn.
Getting Aerodactyl δ out can be troublesome. Mysterious Fossil can't be searched for by your usual Supporters or Balls, Holon Fossil can whiff on a bad flip, and Scott into Strange Cave into Professor Elm's Training Method for Aerodactyl must be done over 2 turns.
Item Search gets a Pokémon Tool every turn.
Late-game, Aftermath can become a very strong attack. It maxes out at 80 damage, 10 less than Banette ex's Shadow Chant.
Gather Energy accelerates Energy, and Power of Evolution draws a card every turn.
Power of Evolution draws from the bottom of the deck, so it will get Aipom if you Snappy Moved and didn't shuffle from another effect, and it will NOT get a card that Magcargo Smoothed Over.
Ledyba's Call for Family gets Grass-type Basics from the deck. When it evolves into Ledian δ, Prowl is a one-time Pidgeot Quick Search. Ledian even shares Pidgeot's 0 Retreat Cost.
If you can get {M}{C} and a Pokémon Tool on it, Ledian δ can use Metal Star, which is a bit like Holon's Castform's Delta Draw with damage tacked on.
Meowth's Plunder can remove Cessation Crystal from opposing Pokémon. After it's done with that task, it can evolve to Persian, who shares Ledian δ's Prowl Poké-Power.