This card is treated as a Normal Monster while face-up on the field or in the Graveyard. While this card is a Normal Monster on the field, you can Normal Summon it to have it become an Effect Monster with this effect.● During your Main Phase: You can send 1 Gemini monster from your Deck to the Graveyard, then add 1 Gemini monster from your Deck to your hand. You can only use this effect of "Chemical Beast Carbon Crab" once per turn.
Use Carbo Crab's effect, either through Superalloy, or Supervise, and send your high level gemini monster from your deck to the graveyard. Then take Blazewing Butterfly so you can special summon the high level later. A faster combo with an ideal hand would be to normal summon Carbo Crab, equip him with Supervise and activate its effect by sending a high level gemini monster to the grave. Fusion summon Superalloy using Carbo Crab from your field, then special summon the high level monster from Supervise's effect.
Sends from your Deck to your Graveyard / Adds from Deck to hand