Cards that allow multiple attacks, such as "Double Attack", are helpful in swarming the field with "HERO" monsters.
This card is great for getting rid of cards like "Gorz the Emissary of Darkness" and "Tragoedia". If there is an EARTH Attribute "HERO" on the field and the opponent Special Summons one of those two, assuming the monsters won't be attacked over this turn, play "Mask Change" on the EARTH "HERO", Summon "Dian", attack over the opponent's monster, and get a new "HERO" that can also attack during this turn.
If you have extra "Mask Change" cards in your hand when "Masked Hero Dian" is on the field you can use the effect of "Masked Hero Dian" to Special Summon "Elemental HERO Wildheart" (attack with "Wildheart" if you want) and then play "Mask Change" to Special Summon another "Masked Hero Dian" with "Wildheart", attack a monster and use the effect of "Masked Hero Dian" again.
You can use the effect of "Masked Hero Dian" to get "Elemental HERO Ice Edge" to destroy a set card in your opponent's Spell and Trap Zone.
Special Summon "Elemental HERO Shadow Mist" to add either "Mask Change" or "Form Change", then you can use it on "Masked HERO Dian" to summon another Masked HERO in the same battle phase.