SeriesBase Set ReleasedJune 16, 1999 Cards64
Not going to claim I know everything about this topic but Ive picked up a decent amount of information regarding these cards in the past two years while researching one of the half decks mentioned here
The mechanic seems to have a bunch of challenges, but perhaps the biggest is that successfully Melding seems akin to a Planeswalker going ultimate: its hard and super splashy, but the reward is so powerful that the game will probably end before you actually get to use your new game piece
But Undead Warchief is still among the very strongest
In that regard, even if you do have luck with card draws and your opponent doesnt break your combos too much, theres still an innate puzzle element forcing you to read your Extra Deck cards thoroughly to make sure you use them right (or, alternately, figure out which ones to summon, and against what)
These new Mega Evolution ex cards take 3 prize cards when knocked out