In addition to giving you the option to switch your Active Pokmon with 1 of your Benched Pokmon, you have the option to instead have your Pokmons attacks to 30 more damage against Pokmon V (V, VMAX, VSTAR, and V-UNION) and Pokmon ex during the turn that Kieran is played
You need to understand how Poisoned is applied, which cards have this ability, how to cure it, and which decks exploit this effect in the current metagame
Matsuno's Fidough card is one of their best, if a little existential, showing the Pokemon looking at pastries in a bakery window that look just like it
Chaos: Whenever you roll Chaos, create a 4/4 white Angel creature token with Flying
This can allow you to take advantage of potent graveyard synergies while inconveniencing opponents, preventing their permanents from sticking on the battlefield
LOADS of stuff came along and burnt brightly for a very short period of time in that early-2000s time though