This Toa came through the time hole created by the time orb. The hole was summoned by Pulsar and consumed the poor Matoran but saved the Toa from drowning. Now Vahi, who wears a custom built Kanohi of Time crafted from the time orb, has to save the past to allow a peaceful future. He carries a Timer Blade and a Santok Launcher loaded with Slowdown Santoks.
This is your best one so far. However, the mask (however cool and well built) is too large, I think you should try and build a larger, or more armored toa.
and "the toa that came from the future to save the past" is sooooooooo corny :P