The first Card in line is Polymerization:
Send Fusion Material Monsters that are listed on a Fusion Monster Card from your hand or your side of the field to the Graveyard, and Special Summon that Fusion Monster from your Extra Deck.
Polymerization offers one of the simplest ways to Fusion Summon a monster. Probably its most important ruling about it (if not the only one) is that Fusion Summons never use Fusion Materials as a cost, as we mentioned in a previous article, so if Polymerization is negated, you do not send any monsters to the Graveyard. Similarly, Polymerization doesn't target anything, so upon activation you do not need to reveal any Fusion Materials or any Fusion Monster. You do need to be able to Summon something upon activation, otherwise you cannot activate this Card. If the Fusion Monster you intended to Summon is no longer in your Extra Deck, or the materials are not sufficient, you still Summon any available Fusion Monster.
A fun fact about Polymerization is its first text: "Fuses 2 or more Fusion-Material Monsters to form a new Fusion Monster.". What do you make from this? Its text makes no sense! Some times, errata are heavily needed Q_Q
Next, we have Magic Reflector:
Select 1 Spell Card that remains face-up on your side of the field and put 1 counter on it. If the selected card is destroyed, the counter is removed instead of the card being destroyed.
Pretty much the prototype of many other Cards with a similar effect of skipping destruction thanks to a Counter. Magic Reflector targets 1 face-up Spell Card you have. You can only target Equip, Continuous, and Field Spell Cards. Not only because of Magic Reflector's Spell Speed of 1, but also, because other Spell Cards do not remain on the Field. The Counter doesn't have a name for itself, so make sure you can tell it apart from other Counters like Spell Counters, the Counters generated by the various B.E.S. monsters, etc. The Counter itself has no effect: The protection is set by Magic Reflector's effect. Finally, this Counter does not protect Spell Cards from being destroyed by Game Mechanics, so if Swords of Revealing Light has expired, or if a Field Spell Card is replaced, the Spell Card is destroyed anyway.
Moving on, we have Cost Down:
Discard 1 card from your hand. Downgrade all Monster Cards in your hand by 2 Levels until the End Phase of the turn this card is activated.
Nowadays, there are several Cards to modify the Level of a monster thanks to Synchro Summon support, but back in the day, this was one of the few ways to do so. Discarding 1 Card is a cost, and Cost Down doesn't target anything. Instead of affecting some monsters, it creates a condition that reduces the Level of any monster that exists in your Hand by two. This affect any monster at your Hand at the time Cost Down resolves, and any monster that you add to your Hand later from any location (drawing it or recovering it through Beckoning Light). The monster's Level is still reduced if you place it on the Field, but not if it is sent to the Graveyard.
Another Card in this Duelist Pack is Ring of Defense:
You can only activate this card in response to the activation of a Trap Card effect that inflicts damage. Make the effect damage of that Trap Card 0.
This Quick-Play Spell Card is chained to a Trap Card that would inflict damage. You can't activate it during the Damage Step, so you can't reduce the damage caused by Cards like Attack and Receive. Ring can only affect a Trap Card if it is chained directly to it. Note that Ring can affect a Continuous Trap Card if it will inflict damage upon activation (like Type Zero Magic Crusher), but it will only reduce the damage once. If Magic Crusher's effect is activated again later, it will inflict damage as usual. Most importantly, note that you can only affect Trap Cards that use the chain (this means that you can't use it against Cards like Coffin Seller), and most importantly, Cards that do inflict damage. For example, Dimension Wall uses the chain, but it doesn't inflict damage by itself. Instead, it redirects the Battle Damage that a player will take. Finally, Ring only reduces damage, so it doesn't stop any other effects that the Trap Card may have. For example, Magic Cylinder will still negate an attack, and Ceasefire would still flip monsters face-up.
The last Spell Card is Fiend's Sanctuary:
Special Summon 1 "Metal Fiend Token" (Fiend-Type/DARK/Level 1/ATK 0/DEF 0). It cannot attack. When this Token battles, the opponent takes any Battle Damage its controller would have taken. Pay 1000 Life Points during each of your Standby Phases. If you do not, destroy the "Metal Fiend Token".
A very simple effect of Summoning a Token. It's worth noting that Tokens are always treated as Normal Monsters, so every ability and restriction listed in this Card is a condition set on the Token and NOT the Token's effects. Using Skill Drain on it would have no effect (mainly because it is a Normal Monster). Reflecting Battle Damage doesn't use the chain. Paying 1000 Life Points or destroying the token is a Maintenance Cost. And just as a random side note, I don't know why, but many people think that the token is not destroyed by battle, even me quite often Q_Q
Interdimensional Matter Transporter:
Select 1 face-up monster on your side of the field and remove it from play until the End Phase of this turn.
A really long and complicated name for a simple effect (with equally long and complicated ramifications). IMT targets one face-up monster upon activation only. Then, during the End Phase, the monster is returned to the Field without using the chain. Note that this is NOT a Summon, it merely returns the monster to the Field, so this Card works even for Nomi monsters like Elemental Hero Absolute Zero or Judgment Dragon. There are two Cards that do not mix with Transporter: The first one are Monster Tokens, which cease to exist once they are Removed from the Field. The second one are monsters that Remove themselves from Play when they are Removed from the Field, as they will not return to the Field during the End Phase.
Other than that, IMT creates some really funky interactions with some conditions and information set "on the monster". For example, a monster affected by Gale the Whirlwind will restore its ATK/DEF to normal, and a monster Summoned by Rescue Cat will not be destroyed. On the other hand, a Spirit monster will still "remember" that it was Normal Summoned this turn, so it will still return to its owner's Hand. These interactions are heavily dependant on what each monster does, so it's hard to explain a rule to cover them all. Some are even contradictory. In this case, it's better to check its Individual Rulings and Card text.
Next, we have Cloning:
Activate only when your opponent Normal Summons or Flip Summons a monster. Special Summon 1 "Clone Token" that has the same original Level, Type, Attribute, ATK, and DEF as the Summoned monster. When that monster is destroyed and sent to the Graveyard, destroy this token.
Another Card that creates a token. This Normal Trap Card responds to a successful Summon, targeting one face-up monster. Once again, copying the parameters and being destroyed are conditions determined by the Trap Card, and not effects from the token.
Finally, we have Return from the Different Dimension:
Pay half your Life Points. Special Summon as many of your removed from play monsters as possible. During the End Phase, remove from play all monsters that were Special Summoned by this effect.
Paying half of your Life Points is a cost. Payments are rounded down, so if you need to pay half of 1025, you pay 512 (and end up with 513 Life Points). Of course, if you have 1 Life Point left, you pay zero Life Points, you cheapskate. Return does not target any monster: You count your available Monster Card Zones when it resolves, and then, you choose as many monsters as possible to Special Summon at once. During the End Phase, all monsters are Removed from Play at once without using the chain. If a monster is no longer face-up, it is not Removed from Play, but the remaining ones are. Finally, if Imperial Iron Wall is active, you can activate Return, and the monsters won't be Removed from Play.
And that's it for Kaiba's S/T Cards. If you have any questions, feel free to drop me an e-mail at ness00[at]gmail[dot]com.