In short, if there are eight or more creatures in play - and there usually are in multiplayer Commander games - then this spell only costs one mana
Effects that modify a creature's power and/or toughness, such as the effect of Jump Scare, will apply to that creature no matter when they started to take effect
But you arent necessarily forced to use the abilities immediately either, which means that attacking with an untap cost creature with a combat trick in hand can goad your opponent into unfortunate blocks
Avatar of Might Big, green, odd
Thats pretty impressive for a game created by a single game developer, Pavel Kolev
Enchantment Tectonic Giant Whenever this creature attacks or becomes the target of a spell an opponent controls, choose one This creature deals 3 damage to each opponent