When an opponent's monster declares an attack: Special Summon 1 "Vijam the Cubic Seed" from your Deck, and if you do, change the attack target to it, and perform damage calculation. If your opponent's LP are at least 2000 higher than yours: You can banish this card from your GY; Special Summon 1 "Vijam the Cubic Seed" from your hand, Deck, or GY, then, if only your opponent controlled a monster when this effect was activated, you can Special Summon up to 2 more "Vijam the Cubic Seed". You can only use this effect of "Cubic Ascension" once per turn.
