One of the most difficult challenges I have completed from any game so far. I started playing Trials seriously about 6 months ago, and despite a few minor breaks, it took almost the entirety of that time to get to the point I'm at now. To access the hidden ninja portals, you are required to get to the end of an extreme track without faulting and bail out across the finish line into a secret portal, you are then teleported to the ninja variant of the same track with your time intact.
Thumbnail credit: Ryan / Plandiss
Meteorain was the real showstopper amongst all of the tracks, taking 8 times longer than the second hardest track. The timeouts listed below also don't necessarily reflect the difficulty, because I approached some tracks at different points in my skill progression. I generally tried to do the next most difficult track in order, so had I done nearly any of the tracks after I completed Meteorain, I likely would not have timed out nearly as many times.
I have listed the tracks in the order of difficulty (in my opinion) rather than the order they show up in the game. I've also tried to cut out most of the faults, otherwise the video would have been absurdly long.
Track name / My Difficulty Estimate / Timeouts / Timestamp
Eye of the Storm / Easy 1 / 0 Timeouts / 0:50
Rock of Rages / Hard 1 / 0 Timeouts / 5:21
Light City Run / Easy 2 / 1 Timeout / 11:11
Robot Wasteland / Mid 2 / 1 Timeout / 15:13
Frostbite / Hard 2 / 7 Timeouts / 19:41
Way of the Machine / Hard 2 / 7 Timeouts / 25:20
Deluge / Easy 3 / 5 Timeouts / 35:05
Devil's Beak / Mid 3 / 8 Timeouts / 39:39
Charred Remains / Hard 3 / 12 Timeouts / 48:04
Inferno IV / Hard 3 / 12 Timeouts / 53:00
Extraterrestrial / Easy 4 / 10 Timeouts / 59:27
Meteorain / Mid-Hard 4 / 82 Timeouts / 1:05:48
There is no official ninja portal for Alca-Trialz.