Note: This is another in my sequence of post-Mystery-Hunt cryptics, which started with "Still There," "Post-Game Predictions," "The Sequel," "Power Lines," "A Lesson in Cryptography," "Yet More Villainy," "Further Escapades," "Time X*X," "Honeymoon in Segas," "If At First You Succeed," "Another One From The Vault," "Next Winter: Wonderland," "DAB," "Some Extraction on the Side," and "Another Campaign"; this one was written before the 2019 hunt and refers to the 2018 hunt. "NI2" and "NI3," as is usual in the National Puzzlers' League, indicate the second and third editions (respectively) of Merriam-Webster's New International Dictionary.
Oh, no — the Health and Safety coin has hard metal edges! For safety's sake it must be embedded in some softer, non-metallic material. Eight Across answers might be suitable, being more "fluffed-up" than the condensed entries you will put in the grid (one condensed entry is a two-word exclamation). Eight other Across clues have wordplay yielding a letter sequence where one letter has been replaced by three; write each replaced letter above each of its three replacement letters below:
to see what such materials are called, who might create such materials, and —
[We suddenly switch to the Control Room, where this cryptic is on a big screen, and beings in five of the seven rainbow colors are reacting to it emotionally.]
Green: Ugh! The start of that intro reminds me of that gross old Island of Personality that connects to the ones from last Janu— Hey, each of you just made Terry misenter five Down answers! And those altered entries include five phrases or hyphenated expressions, including one that's NI2 and one that's NI3! Yuck! [Walks off in disgust.]
Blue: Sigh … Remember how on that island, Terry had to let some things evolve, and it was sad to say goodbye to the old ones even though the new ones were clearly related, and enhanced (in a specific way) by exactly 60%?
Violet: I was just scared of the strange, alien creature Terry encountered there; it was so weird, and unearthly, and all those other anagram indicators!
Red: And it was so unfair! The whole island was themed around a series of awesome load-in hacks, getting in just under the dome, and Terry didn't get to be the one doing any of them!
Yellow: But it was such a fun game, where Terry got a prize at the end that was gold, just like me!
Blue: But it's gone now. If Terry circles the nth letter in each Down clue whose entry has n non-rainbow letters, the circled letters in each of our five-clue groups (in clue order) will spell a word, and these four words (in our speaking order) will say what bygone activity the island represents.
Violet: And the creature's been replaced by an even scarier, two-peaked mountain; in the grid, she can circle each "replaced" letter (as per the intro) to draw it, and climb it bottom to top to see its name!
Red: And to conquer that *&#%! mountain she'll have to reach two more goals: the peaks themselves. Each, left to right, will identify what it is, and applying the blue and violet changes to the left-hand one (using exactly the appropriate-length violet change), and the red and yellow changes to the right-hand one … will give two nonsensical letter-strings! Arrgh!
Yellow: It's all fine; Terry just has to look back on this island's memories with complex, mixed emotions. In each of four Across clues, one word must repeatedly have mingled sadness and fear change to mingled anger and joy before solving; in four others, in tribute to our green coworker, one word must have its (four-letter) stomach turned. She can put the two letter-strings together, and apply both these changes to the result, to see who can definitely tell her how to win —
[We switch back to our original perspective.]
— what teams win by finding coins at Mystery Hunt!
ACROSS
1. Deviously sells tees lacking a ferrous alloy [NI3]
6. Maiden characters from booklet Paul's reading would upset antelopes
11. What's held back by rabbi (i.e., Curtis) resembles extra-dense frozen
water (2 wds.)
12. Ohio-dwelling actor Cage twice twirled singer Cole and writer Fleming
13. Nez Perce's leader goes into NIH figures
14. Loveless Roy's donning garments lighter than some pili for
an assignation
15. Satie, who composed duds for groovy New York natives
16. Honked excessively at Theodore
17. Tintin randomly bestrides horse after horse. (That was a clue!!!)
(2 wds.)
20. British car's trunk and bisected engine produce bouncy sound
21. Did puzzles, with the last couple turning painful
22. Note author with mini losing heart
25. Agree rolling seas would overwhelm dowsing rods? (2 wds.)
27. Floor-scrubber keeps B/W television's lid on
30. Ax gutless Jeff; he's hurting feelings
32. Looking only at the Firemist Silver automobile raconteur Abrams shows
singer Bareilles
33. Unhats, after unveiling and advancing Henry's trig func.
(abbr.) [NI3]
34. When imbibing port on the Red Sea, act numb
36. Satellites orbiting Mr. West and Brigham Young, et al.
37. Toss bun at people 2000 miles west of the isle of the bygone Didi
38. Short film on hosp. facilities containing snakelike fish
(hyph.) [NI2]
39. Cold duo from Quebec pans fun runs (hyph.)
40. Nickname of coders inwardly accepted by Andy after the start
41. German "Y" sans athletic facilities
DOWN
1. Dale's discarding good optical equipment
2. A fen described by notes
3. Cat ignoring grand row
4. Women with knighthoods are finally wearing clogs
5. Floundering, rote Rent
6. Times supporting Kay, Kevin, and Eartha, who sang
7. Now rotate three lines joined at a point
8. To chastise with a humorous remark is hard
9. A writer who writes sardonically about French dictatorial power
(2 wds.)
10. Troll takes in the finale of Get Smart
18. Group of accepted works a ball-hurler mentioned
19. Are intruding on editor with sound detectors
20. HBO blocks Yiddish interjection that thrills me (2 wds.)
23. Barnabas electrifies partly Swiss city
24. Extraterrestrial, antler-capped insect
26. Told what a farmer does with stitches
28. Tense, frantic adolescents
29. Some small animals Mike extracted from shoes
31. In bygone times, Dad evacuated Somerset
35. Say a little something about a castle