Flavorfully, it's an amalgamation of five other artifacts that split back up into its individual components when it's dealt with
The current mulligan rule works like this: If a player has no Basic Pokmon in their opening hand, they reveal their hand to their opponent, shuffle it back into their deck, and draw a new hand (and repeat this process until they do draw a Basic Pokmon)
In addition to potentially allowing you to cast an opponent's strongest spells for free, Tasha's static ability creates 3/3 Demon tokens whenever you cast a spell you don't own, converting these stolen spells into additional manpower
Each player must have an active Pokmon, and can have anywhere from zero to five benched Pokmon that can be swapped in if the active Pokmon is knocked out or swapped out
With its Blizzard attack, it can deal 80 damage to the opponents Active Pokemon and an additional 10 damage to each of their Benched Pokemon