If you check milestone 6, 12 and 18 next to man-thing you see 3 minion crystals.
The crystals are sent to your special crystal tab. Very bottom under the solo crystals.
I do not have them in my rewards. I took a screen recording video but I can’t post it for some reason
You've answered your own question- you were Thronebreaker when the EQ started. Minion crystals are only available in EQ for Paragon+.
Mine are in the main Crystals tab- not Special.