The owners of each powerstone all turn into some kind of powerful beings when they collect powerstones (in the game) it seems that the characters just turn into these beings when they use one in the anime. They scream "Power...Change!!!!" And they turn into whatever they're supposed to turn into. The powersone holders are as follows:
Falcon turns into this red mecha-like being (think of it as a jet plane) and has the attacks "Power missile", and "power explosion" Suffice to say, he has to shout the name of the attack first.
Ryoma also turns into a mecha-like being (think of it as a sword, i guess), except he's white. And he STILL uses his sword. I don't know the attacks he uses.
It turns out that the crystal ball that Rouge has is actually a powersone. Rouge turns into something like a fire-goddess. Her transformation is the coolest, IMO.
When she transforms, Ayame just changes her costume...It's a silly PINK rabbit costume with a 4-pointed star on her back...or was it a flower? Eitherway, it's silly, IMO. And she still throws those dart things (what do u call those stuff, anyway?) But she also has the power over water. That's the cool part of it, i guess.
So you're asking how one attacks as a TOTEM POLE? (visualize a tall carved LOG that bonks you on the head and calling it a "wings of justice" attack...*sweatdrop* That's just a joke^_^) Garuda will fly high in the air, then a pair of golden wings will suddenly appear from his back ...and then he'll dive...and dive...and dive...and dive...until he hits. The other attack (it think it's Light of Freedom or something) uses Gold light instead of wings. See the difference? Maybe not. Just watch the show!
Wang Tung turns into a wooden (but flexible) human. He has some attack that concentrated his energies into a ball, and he throws it (sorta like Gaokou's Kame Hame Ha).
Valgas is the final boss in the game. Remember the altar with the stones on them in the intro, that's where they fight last with a big beasty. The same thing goes for the anime: he's the evil, greedy boss.
Other characters:
There's also Apollus, the old guy that shouts "YOUNG MASTA~~~" and chases Falcon around...Actually, when i saw Guwakubo (Steam Detective), who calls Narutaki "Young Master", he reminds me of Apollus...And they BOTH remind me of Alfred (as in Bruce Wayne's Alfred)
Kikunojo is Ayame's *transvestite* brother...He's really funny, especially when he's all over Falcon..and when Gunrock proposed to him! *falls off the chair laughing* Oh geez!
Jack the mummy man with knives. I don't know where Jack came from. His mom WAS the owner of Falcon's Power Stone (see, she died in a fire and Falcon's dad found the Stone.)
Wang Tang's master reminds me of Tokaki-sensei^^ I think his name is Wu something....
The first arc of Power stone revolves around Falcon trying to find his dad, who is trying to unravel the secrets of the Power stones. And he meets all the other holders of the stones along the way. It sorta kinda reminds me of the concept in Ranma 1/2 where almost all the opponents become the main characters' friends. 'Coz Falcon ALWAYS ('cept for Rouge) fought against the other holders before they both realize that they shouldn't fight^^
The second arc is abt Falcon going around the world looking for his friends again, and trying to look for the guy trying to assassinate them, who happens to be Falcon's all-time hero, Valgas, the man himself. Valgas kinda reminds me of Nakago...They're defeated the same way, too^^ In the final battle, it's a showdown between Valgas' Dark Stone and Falcon's Light Stone. The light stone is the product of the combination of all 7 power stones.