Great search card for decks that heavily rely on fusion monsters.
Costs nothing to activate and can give you a plus 1 in card advantage.
Being a trap card slows down its usage.
Other Fusion Support cards
Fusion Recycling Plant can recycle 1 fusion material monster to your hand, and also search for Polymerization from your deck. King of the Swamp can be treated as 1 fusion material required for Fusion Summon, and at the same time it also can be used to search 1 Polymerization from your Deck. Fusion Sage can search 1 Polymerization from your deck.
Here are decks that rely on fusion summoning, making Fusion Reserve a great search and consistency boosting option. Although in the case of Gladiator Beasts you only use this card for its search effect, you cannot use recover polymerization from the graveyard as Gladiator Beasts generally don’t use fusion cards.
Red-Eyes Slash Dragon
Ultimate Ancient Gear Golem
A to Z
Reveals your Extra Deck / Adds from Deck to hand / Adds from Graveyard to hand