For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty and only if you have an available land play remaining
Solgaleo-GX did, three years later, in one specific rogue archetype, and only because, due to a technicality, it's still Standard legal outside of Japan)
by Legendarys_Andy Set 13 Core Midrange Libertalia Attack of the Vine
If the gift was promised, you choose which creature card to return to the battlefield while Starfall Invocation is resolving
Because if you're gonna break the game, you might as well shatter it
Throw in some pump spells like Become Immense and Mutagenic Growth, and you have the recipe for a deck that can potentially 20 the opponent in just a single attack step