The ability triggers anytime you deal combat damage no limits like once per combat or once per opponent. Whats more, he has this text on either side of his transformation, ensuring youll always draw cards provided you can get through
Its also cool regardless of whether you play Magic or not, which is a plus in my book
Let's say that you build a deck where your only creatures are one copy of Street Wraith and two copies of Emrakul, the Aeons Torn (just in case you happen to draw one of them)
Honestly, it's fairly comparable to Swiftfoot BootsSwiftfoot Boots which is played in a staggering 118,000 decks
Similarly, replacement effects that modify how creatures you control enter the battlefield will see Arixmethes entering as a creature rather than a land
In the past 3 weeks I've spent well over 26 hours (I kept track) researching Pokemon and Pokemon cards