• Make sure to remove from archive plinths "Mages' [type] Work Spells have a [x]% chance to do +[y] per cast." powers. I'm not entirely sure how they work but I suspect they don't help level mages so best to eliminate it as a variable.
  
• Don't even bother to attempt this achievement unless you have a "Triumphant Trials" "+150% Trial XP" active plinth power via an archive. The easiest way to get it is to grind the second infinite hall for it. I believe it has a chance of spawning in the 6th and 7th rooms.
  
• I highly recommend having the "Relic of the Founder" on an active plinth and making the Founder teach in the Advanced Classroom. This will make basic skill fulfillment very fast.

Do NOT equip your target mage with any +skill relics because they have to fulfill those imposed requirements before they can be promoted to staff. That's antithetical to the achievement's goals. You can attenuate relics to them (time permitting) but just make sure it isn't those.

Highly recommended doing 5 out of 6 of the Shattered quests from the Ember Dragon called "Stay or Go." This mission takes 2.5 days (make sure to prepare for "Advice to Head Out") and it grants 100,000 XP. This is enough XP to instantly take the Apprentice from level 16 upon becoming staff to level 18 right after becoming staff, skipping the grind.

"Final Gambit" will work too which is the final quest for Raven Cultists but it is 3.5 to complete instead of 2.5. To do that one, you need 10x of Crystal Portent and 10x of Crystal Prophecy.

Make sure to have Tier 1, 2, and 3 wands crafted and ready to go before starting this. I have chests next to each upgrade device with wands filled for that type to completely eliminate travel time.

You have found the Ember Dragon and the Altar of Fate in the Underschool.

This guide assumes you already have a complete mage school with Advanced Classroom, all seven magic specialization rooms, Archive rooms, and House Commons. See below for the state of my mage school when starting this (relaxed difficulty, 3x resources, and Freeform layout)

• Do the prep above.
  
• Complete all skills and accumulate enough XP (just completing the silver trial is enough) to make apprentice (3 star).
  
• Make them an apprentice in the same skill they started with (e.g. dark -> dark) to raise the XP limit.
  
• Upgrade wand to tier 2, then tier 3.
  
• Complete all remaining trials. If the trial is not something that can be done quickly, replace it at the Altar of Fates. Completing all trials should reach the cap of 12.
  
• Let them attend classes to fill out their skills. Create custom schedules for them and their teacher to get as much class time as possible.
  
• When they reach 12 star, promote to staff.
  
• Send them on "Stay or Go" or "Final Gambit" quest.

1. Summon a gifted mage. Doesn't have to be gifted but if you're gonna put the effort in, why not make it a keeper?
   
2. Note the date and time when the summon music plays. You can get the time by hovering the mouse over the hourly graph on the bottom-center of the screen.
   
3. Re-roll all of the trials that can't be completed immediately for something else that can be. This is going to vary based on your school set up. I rerolled two of them ending up with: Dancing With Friends - Bronze, Attuned - Bronze, and Group Diner - Silver. Everyone in my school eats and dances in the same House Commons so every night, group dancing and eating pop. I choose Attuned because it would only take a few in game hours and isn't dependent on anything else.
   
4. 5:18 my gifted dark mage spawned
   
5. 18:00 both trials were changed and all skill training complete
   
6. 19:13 first trial completed for eating among 6 people; level up to max because this was the silver trial.
   
7. 19:50 second trial completed for dancing among 6 people;
   
8. 21:22 the chosen one completed Dark Apprentice training. I choose the same skill as the base skill so they'll mostly only have to train in one. The moment training was done, she immediately hit the next level cap because of the completed silver trail.
   
9. I had two other Dark Apprentices that would lengthen training time for the chosen one so I made sure to get them out of the way (graduate, dismiss, or expel).
   
10. 21:25 ordered tier 2 wand upgrade to raise the XP cap again. This speeds up training by increasing power. It also shows us what the gold trial is.

1. 1:20 ordered tier 3 wand upgrade.
   
2. 4:30 (almost 24 hours) wand is fully upgraded but sadly I got Neatnik and Nurturer for trails so will have to replace those. My alter of fate was in use by another mage so I ordered my apprentice to complete the tuning trial.
   
3. 6:53 tuning complete so 3 of 5 trials are done.
   
4. it's normal class time dark mages so I let her attend class.
   
5. 11:00 scheduled to sleep so I let her do that. Dark skill level is 462 on level 4 of 8 at this point. Needs 1 point trained in water and 2 in nature as well but that won't take long as long as the classes are available.
   
6. 18:00 wake to eat then recreate but instead of recreation, I ordered her to replace her Neatnik - Gold with Warder.
   
7. 20:47 Warder - Gold gained, resupplying with mana then hammering the Underschool Ward.
   
8. 22:43 Warder - Gold completed which raised her from level 6 to level 10
   
9. 23:00 classes start so I let her do that as normal

1. 6:00 is scheduled eating time which I let her do.
   
2. 7:56 she's done eating and is back to casting dark magic in the classroom.
   
3. 11:00 she's scheduled to sleep. 5 of 8 levels in dark magic, 1780 of 3200.
   
4. 6:00 again, she's scheduled to eat which I let her do.
   
5. 19:01 she finished eating and instead of recreating, again, I ordered to replace Nurturer - Platinum with Blissful Learner (cast 100 times at >75 conviction).
   
6. 20:50 she has Blissful Learning. At this point I created a special schedule just for her where it's all class except 13-18 which is sleeping for 5 hours and 18-19 which is eating for 1 hour. I did the same to her level 8 teacher.

1. 6:45 she completed her final trial maxing out her level at 12. She's at 6 of 8 levels of dark magic, 1280 of 4800. I also graduated out the last of her competition for the Dark Apprentice training equipment.
   
2. 7:48 I ordered up a new slate of 7 initiates (one of each type) to keep the beasts satisfied. They will not be upgraded to Apprentices until the achievement is complete.
   
3. 13:15 bed time: 6 of 8 (3567/4800)
   
4. 20:00 napped, ate, and back at class.

1. 10:19 the teacher took off to eat while she was recharging mana so instead of doing dark training, she went off to do nature training which was currently in session.
   
2. she got exhausted and wanted to sleep. I overrode that command to finish nature training while she's here.
   
3. 12:25 she went to sleep ahead of schedule because she's exhausted: 7 of 8 (3180/6400)
   
4. 14:19 the school has been eradicated of all apprentices except the one for the achievement.
   
5. 19:46 back to dark class.
   
6. I double checked "Stay or Go" quest is ready to launch including positioning the 4 mages that are to go. If you're not ready to do it, now's your last opportunity to prep it.

1. 6:11 she finished dark mage training and left to finish water training which the Founder is set to accomodate when outside of regular class hours.
   
2. 6:46 all training completed. Hire her! And delete those custom schedules.
   
3. 9:23 One of us! One of us! One of us!
   
4. Since there's plenty of time left because of my 100,000 XP plan, I decided to attune the rest of her slots before sending her off so the attunments will benefit from that huge XP hit.
   
5. 17:00 she was going to pass out from exhaustion while attuning the final relic so I let her sleep and eat.
   
6. 19:29 instead of recreating, I had her finish attunation.
   
7. 22:33 4 x level 24 relics attuned, time to start "Stay or Go": level 16, 16.3K of 17.7K XP.
   
8. 23:49 the Ember Dragon departed with my Cram Session mage and three others. It'll take 2.5 days so...business as usual until then!

1. Achievement poped the moment I "Click to Complete!"