Congrats! I rented a Maiden Pro to add to my collection during COVID... I've gotten to Tomb #9 thus far. SOooo close.
I only had two of the Level 2 Eddies, so it left me with three. And I was missing two Shards. I got one of them replaying a mode, and tried going for a Level 3 mystery to get my last shard, but failed.

Unfortunately, Mummy SJP (and 2x SJP for level 2) is more difficult on the pro -- no single-ball Mummy play for me.

Indeed and agreed. I use staging constantly on that flipper during all multiballs, and especially to open up the L orbit spinner shot for switch hits for next Mummy JP.

Run to the Hills... achieved! Great feeling. Caught fire and got 4/5 shards on first attempt, mummy and trooper on first attempt, crushed the beast, and an early 6-way combo. Had zero level 2 Eddies, so I had to grind out drops to get my Mystery Level 3 soul shard on 2nd to last ball, drained. Had RTTH lit before I plunged last ball, and nailed the R orbit before I even validated my playfield.

Now onto trying to get 900M super death blow!

Yes. Factory defaults. Tilt is tight. Outlane widest on one side, and mid on the other (these were the positions as they came from factory). Sling switches adjusted to much more tight (sensitive) than how they came from factory. And this particular operator (that I rented the Maiden from) has his main flippers "flopped" ever so slightly, making it more difficult to cradle and more difficult to hit central shots.
Last: On thick carpet, so I couldn't even do any death saves.

Ouch. Sorry, yeah, that’s a new one... Trooper level 1 Sometimes miss after 1 trooper mb, but never two.

And combo (and super deathblow) scoring gets really juicy when you’re playing your ball that you’ve cashed in Tomb 4. 5x combos and death blows. I’ve gotten the 300M super deathblow, so now I need to get 3x ready, and get the elusive 900M!

This gets into the nuance -- due to the fact that a qualified 3x PF, and a lit Tomb #4 will both carry between balls, whereas a *collected* Tomb #4 and an *activated* 3x PF do not.

- Qualify Tomb #4, but do NOT collect it.
- get 3x PF ready, but do NOT activate it. (If you drain your non-final ball during this step, your 900M Deathblow is still in play.)
- Collect Tomb #4. (You're now "all in," and if you drain, your chance for 900M Deathblow will be gone.)
- Complete a 6-way combo, with one of the ramps as the final 6th shot.
- Use the ramp return to go over your lit inlane to activate 3x PF.
- Cash in your Super Deathblow at either the Revive spinner or the Bulls-eye target (must be the true center of the bulls-eye).

Normal Deathblows re-award the same value as your highest Combo award of that Combo sequence, if the deathblow shot is hit as final shot of the sequence.
But Super Deathblows give 3x of a normal Deathblow.

A 6-way combo awards 20M as its 6th shot award.
Having Tomb #4 gives 5x that, so 100M as 6th combo shot award.
Finishing the sequence with a Super Deathblow gives 3x 100M = 300M.
If you have 3x PF running, then you get the massive 900M.
And don't forget that on your way to the 900M, you also scored at least another 190M in 5x Combos on your way there (without 3x PF).
(2.5M + 5M + 10M + 25M + 50M + 100M)

Tomb #4 is, by far, the most lucrative scoring opportunity in the game. It's untimed and unlimited, but similar to Stern POTC Max Jackpots award, it's only valid for THAT ball.

It's a really cool shot-maker type of combo system. Very different from most other machines combo rules on short timers to reward flow play.
You can certainly do the 6-way in complete "flow," but because some of those shots are so tight, and missing is so punishing... I find myself taking it slow & steady... using drop catches, ski jumps, and a loop pass to get control between every shot except for the L orbit to Big Loop combo.

Oh, and one other thing: just like any other tall task in Maiden that requires completion -- and not just starting (like Mummy MB SJP, completing Rime and Aces, etc.), it's best to throw in a both-sides-lit Revive to improve your chances. Optimal is to light Revive between Steps 2 & 3.

Same. I like to end with a ramp shot, because it gives me the option to activate a PFx immediately prior to cashing in the Super Deathblow. From the ramp shot feed, if it's the L ramp, then I'll take the bulls-eye shot on the fly, because I'm pretty dialed in on the center bulls-eye on the fly from the L flipper. If it's the right ramp, I'll either ski jump it or post-catch the feed to get control before shooting the bulls-eye or Revive spinner.

No. You do not need to collect a deathblow or super deathblow to get the Tomb Treasure for the 6-way combo. The deathblow is just for style points.

The six-neck guitar display is hilariously awesome.
I do wish that the audio guitar riff that accompanies each successful combo went up in pitch/intensity for each higher level of combo.