If the gift was promised and the target is illegal as Valley Rally tries to resolve, it won't resolve and none of its effects will happen
I'll get to this one in more detail in a moment
There are many ways to exploit it along with Sword of the Meek that can go from taking infinite extra turns with the help of Time Sieve or add infinite mana with Ashnod's Altar, making it a solid card to include in artifact and combo decks overall

Cards Between $5-10 The Fire Crystal Sword of the Animist Three Visits Primeval Titan Yuna, Grand Summoner Dark Confidant The Wind Crystal Jodah, the Unifier Genji Glove Nibelheim Aflame Loran of the Third Path Cryptic Command Aettir and Priwen Walking Ballista Command Beacon Tifa, Martial Artist The Earth Crystal Reanimate Y'shtola Rhul Ultima Weapon Cards Between $10-15 Dark Ritual Isshin, Two Heavens as One Tymna the Weaver Azusa, Lost but Seeking Diabolic Intent Vial Smasher the Fierce Lightning, Army of One Summon: Knights of the Round Kinnan, Bonder Prodigy Starting Town Final Fantasy Promos, Alternate Art, and More Final Fantasy is chock-full of alternate versions, with most characters having two versions, 10 of them having three and Cid, Timeless Artificer having 15