The are the Seal Dragons, a lineage of cursed dragons.
[AUTO](RC):[Counter Blast (1)] When this unit boosts, if you have a vanguard with "Seal Dragon" in its card name, you may pay the cost. If you do, until end of that battle, all of your opponent's units cannot intercept, and the boosted unit gets [Power]+2000 for each of your opponent's grade 2 units.