Enhance Monsters are a new type of Monsters made by LHK. They rest in the Extra Deck and they have pink card frames.
To Enhance Summon, you need 1 monster equipped with only 1 Equip Card (by that, it is not only an Equip Spell Card, but also Union Monsters, monsters that can equip on other monsters [see "", as well as the " " and " " archetypes] or even Normal Trap Cards that can be treated as an Equip Spell Card [like " "]. Those cards are sent to the Graveyard and you already did an Enhance Summon.
Enhance Monsters have a Level, so they can be affected by the effects of cards like " ".
Enhance Monsters have two parts of effects. The one is the generic which is applied regardless of the Equip Card. The second effect is the "Enhance Effect" as called by card effects. That activates only when a specific Equip Card(s), which are listed, are this card's Enhance Material. This trend was thrown away in December 15th, 2018 with the creation of "Gaia, the Powered-Up Knight", an Enhance Monster that does not have that trend, and future cards continue that concept.
For a list of Enhance Monsters see "List of Enhance Monsters".
Double Enhance is the action of Enhance Summoning from the Extra Deck using 2 Equip Cards, both equipped on the same monster, and using said monster as a material. Monsters Summoned via Double Enhance have effects if either one of the two specific cards listed were used for that Summon.
"Aurum Silver Knight" is the first monster that makes use of the Double Enhance Evolution. Similarly to the above, that trend was thrown away for an unknown future evolution.
- LHK declared that the colors for the Enhance Monsters will be pink to differentiate with the red of Composition Monsters.