Well, I sure wonder what would be a way for cards to remain in a Spell & Trap Zone besides being set.

RD/KP13-JP013 魔装獣ギアパルド Masoujyuu Gearpard (Magiarms Beast Gearpard)
Level 7 EARTH Spellcaster Effect Monster
ATK 2300
DEF 1800
[REQUIREMENT] None
[CONTINUOUS EFFECT] If there is a card in your Spell & Trap Zone, this card gains 200 ATK, also this Attack Position card cannot be destroyed by battle during your opponent’s turn.