A reference to a Shadow Priest spell from the game "World of Warcraft" known as Mind Flay. It is used as a "filler" answer for any question, as a term of comradery, or as a social greeting.
Tyflayz/Typhlayz is a variation of the word referencing the Druid Moonkin spell Typhoon which is mega-lulzy.
It should be noted that this term originated on the Baelgun server of World of Warcraft, and was repeated many thousands of times by rampant homosexual deviant Pointyears and well-known attention-whore boob-flasher Viviana.
Typical usage in World of Warcraft:
Guild leader: So I did some research as to the exact value of +hit gear on a hemo-specced rogue while using duel fist weapons and I was wondering if anyone knew what the relative AP-dps ratio of SS was with Bloodlust up.
Shadow Priest #1: Flayz
Shadow Priest #2: flayz!
Fat nerd: What the fuck is it with this flayz shit? It's getting old.
Random failure: FLAYZ!
Guild leader: *sigh*