Steelix is a Stage 1 card so you would not necessarily have a stage advantage over your opponent, but heres how the combo worked: 
[26] Cycles[] Core Set 2019 has twelve cycles, one of which is a double cycle, and five of which can only be found in preconstructed products (and subsequently not in booster packs)
If 2 of them are heads, this attack does 50 more damage