Giving your opponent a spell or trap card will make their field smaller for other cards. If you give them a card with a surprising negative effect like Card of Sanctity, they might lose the duel just by activating that.
Select 1 card Set in your Spell & Trap Zone, and force it on your opponent. Only the player that activates this skill can view this card. This skill can only be used once per Duel.
If you don’t force your opponent to use that card, they can simply choose not to activate it. It is not a competitive skill because it is limited to only one activation per duel, so even if you build a deck around it, it is not guaranteed that you will manage to take good advantage out of it.
Its actually a decent effect, especially if you play defensibly. If your opponent sets 2 cards just set a card. usually they'll have some defensive cards like Mirror wall, WallOfD, Spike W/Chain, maybe a continuous spell card ect. (or even if they activate a equip spell, but thats rare enough)
I built a 'gift' deck Using Gift Exchange and Card exchange, its really fun to play as. Its pretty good against certain meta decks If played right.
The card I like to give isn't "Aegis of Gaia", its good, But I like "Localized Tornado" Because its a trap card, they will remind them to use it I find more people fall under the pressure using it more that way.
You can olso give your opponent cards that are only activate their effect when destroyed. So you make one of your opponent's spell/trap zone useless and not yours until you storm everything. Also the oppenent my destroy them to free his zone. But it is still only once per duel.
This skill and Xing Zhen Hu + Judgment of Anubis is the ultimate lockdown strategy. Your opponent will not be able to use any spell or trap cards during the entire duel. Even if they play Twister from their hand to remove your trap you counter it with Magic Jammer / Judgement of Anubis!
This is why I love Tea <3 Or another excellent combo is the Unhappy Girl with Holly Guard which is a free ability. You run two of these traps to lockdown the trap zone then the Unhappy Girl and some defense position force change cards to also lockdown their monster zone. Totally evil!
To play a quick play spell they would still need a free spell trap zone.And there are some monsters that have the ability to empty spell trap zones, like that one wind bird with a flip efect to return 2 spells traps to the hand and the toy magician with the ability to destroy them