I've created a two-part 100% walkthrough video. It covers every single achievement in the game except the co-op ones and the speedruns, but the co-op are self-explanatory and the speedruns are super easy once you've played a level, since you can usually just run past everything and solve the puzzles most of the time. Contrary to some reports, you CAN get the gold points challenge on EVERY tomb on your first time through in solo play. Follow along with the video below as you play through the game (and part 2) to have your 1k in 8-10 hours tops. A detailed text guide follows after the time stamps for those that prefer it, copied over from the walkthrough I've written for this game.
This achievement is story-related for defeating the Oracle of Osiris.
Timestamps:
00:07 - Pyramid of Osiris
13:32 - Tomb of the Timekeeper
22:08 - Challenge Tomb #1
25:00 - Tomb of the Silversmith
35:42 - Challenge Tomb #2 (west/southwest from Tomb of the Silversmith)
37:55 - Khepri's Tomb
42:52 - Oracle of Osiris
46:50 - Challenge Tomb #3
49:50 - Tomb of the Ferryman
1:02:22 - Challenge Tomb #4
Head down to the Oracle's chamber and enter. This area has lots of green insta-kill vents, and eyeballs on the pillars. Head down the first set of stairs and kill the enemies, then bomb the eye. Go through the vents and place a bomb by the switch. Shoot the switch so that the lower left vents on the wall shut off, and use the grapple point to climb up between the two rows of vents. Detonate your bomb with
to turn off the upper-right vents, and finish climbing up. Bomb the eye to the right to shut off the vents around the corner.
This next part is tricky, so don't get stressed if you die a few times. Place a bomb by the switch and shoot it. Connect to the grapple point, but don't drop off the ledge just yet. Stand right above the disabled vents, and drop off. RIGHT as you drop off, detonate your bomb so that the switch activates, turning the vents back on above you and disabling the ones to the left before you hit them and die. Hit hte pressure plate, go upstairs, and kill the eye to the left. Go back down and grab the honeycomb ball and push it back to the beginning area into its receptacle.
Head through the gate to begin a rather lengthy fight against eyes in the floor with lots of adds. Just keep dealing with the adds and damaging the eye in the floor with your remote bombs when you can until the fight is over, at which point you'll unlock Didn't See That Coming.