2 EARTH Machine monsters
If this card is Link Summoned: You can add 1 "Ancient Gear" monster or 1 "Geartown" from your Deck to your hand. You can target 1 Spell/Trap you control and 1 face-up monster your opponent controls; destroy that card you control, and if you do, change that opponent's monster's ATK/DEF to 0 until the end of the turn. You can only use each effect of "Ancient Gear Ballista" once per turn.