DNA Splicers appears in 3 version groups since Generation V, a Gameplay item in the Key Items pocket
PokéAPI item 671 of 2,223, Gameplay category, Key Items pocket
Effect, in PokéAPI's words
DNA Splicers: “Fuses Kyurem with Reshiram or Zekrom, or splits them apart again.”
Games
DNA Splicers is listed in the text of 3 version groups, first in Generation V
Game index by generation
IIIIIIIVVVIVIIVIIIIX
Named in
Black 2 and White 2X and YSword and Shield