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 upon completing the Tomb of the Ferryman.
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
Challenges: Bronze/Silver/Gold – 60,000pts; Complete in under 7:00; Collect 5 Red Skulls; Cross the spike ball river without touching the water, Use the trap platforms to dunk an enemy, Destroy the wall without grabbing the Timebomb.
On your way up to the Tomb of the Ferryman, you’ll go up a long water channel and need to use your staff on the energy orb to the left to lower the spikes. Use your bombs to blow up the arrow traps on the wall ahead, then grapple up. There is a challenge tomb nearby that you can reach via some platforms off to the side if you wish, but the five challenge tombs will have a separate section after all the main tombs. You’ll have to bomb a switch plate outside the tomb a few times until the spinning wheel lands on the sun symbol to open the tomb.
As with all tombs, you’ll now need to do two more playthroughs. For the first run we’ll be getting all the challenges except for crossing the river without touching the water and the speedrun. Also, the alligator enemies here must be knocked down then bombed to kill. At the start, shoot the eye to drop the spikes and place a bomb on it. Go past the first set of spikes and detonate the bomb to drop the 2nd and continue on. Place a bomb in the fast-moving river and detonate it on the eye below to drop the next set of spikes. Then place another bomb in the river, pass the spikes, and detonate it to raise wooden platforms above to reach Red Skull #1/5.
Continue on over the spike pit and around to reach some rock platforms that will fall out from under you as you run over the water below. Swim up to the left and use your staff to lower the spikes. Keep
held until you climb up above. Kill the alligators in the water for extra points. Once you hit the switch on the upper left to raise the platforms in the water, you’ll have to jump diagonally off the one by the Red Skull #2/5 over to the diagonal one to the right in order to grab the skull. If you miss the jump just use the shorter platform to climb back up and jump around on the platforms to get the skull and get back to the proper path. After you cross and see the bomb gator show up, use the blue platform above with your staff to carry you up to the upper ledge.
When swimming upstream, you’ll have to shoot an eye to lower some spikes. At the top of the river, go around to the left and press the switch beside the two glowing orbs to raise a wooden platform on the far side. Rotate the lever to raise the mirror, then jump back across and use your staff’s light beam through the 1st orb, off the mirror, and through the 2nd to lower the spikes on the far side. Continue on, past the alligator that jumps up, and all the way down past Red Skull #3/5 until you find a blue platform and a large ball nearby. Push the ball back up to the left to press the switch, raising a stone path in the water and a wooden platform under the skull so that you can collect it.
Return back down to the blue platform. You must jump to the next platform and press-and-hold
in mid-air to lower the spikes on the next one before you land. Continue holding it until you’re on the non-blue platform then release it. Kill the alligators below using the low platform to the right for more points. Jump to the next blue platform. Jump off, and once again jump and use your staff in mid-air to lower the spikes on the next one before you hit them. Continue on until you see Red Skull #4/5 in some spikes up ahead. Defeat the alligators upstairs and pull out the piston, then rush back down and grab the skull before the spikes reappear.
Continue on past the piston and up the blue platform to the ledge above. The water path to the left has more gems and an alligator for points. You’ll reach a river with tons of spiked balls floating in it. Make sure to only jump across the platforms here to get to the end. If you fall in the water, reload your checkpoint to get the challenge without touching the water when you reach the end. Continue on after this river and you should soon reach the 80,000 points for the gold points challenge if you’ve been breaking everything and killing everything.
You’ll ride a blue platform up and see an eye, a switch, and a long wall of spikes. First let’s get the challenge for dunking an enemy. Hit the switch and shoot the eye, then look for some enemy alligators down below. When the wooden platform is ‘up’ on the left, they will make huge jumps up onto it. As soon as they do, shoot the eye to drop the wooden platform out from under one of him to dunk him in the water and complete the challenge.
Next, shoot the eye so that the spikes above are up and the spikes below are down, then hit the switch to start a bomb moving. Hold
to slow its fuse. Position yourself so that you’re facing the eye that lowers the spikes. Once the bomb nears the smaller blue platform below you, let go of
then press and hold it again quickly to lower/re-raise the platform to launch the bomb, while at the same time hitting the eye to lower the spikes so that the bomb clears them.
Keep holding
to slow its fuse while you use bombs to move it over to the breakable wall, of course. If for some reason the bomb falls off to the left, your timing was off and you’ll need to raise the platform below slightly sooner so that its trajectory doesn’t drift as far left. Shoot the eye one last time to raise the spikes above and lower the spikes down by the larger blue platform below, then drop down to get Red Skull #5/5 in the small alcove behind the platform. The end of the tomb is a simple chase scene. After finishing this first time, you’ll unlock I should buy a boat.