User blog comment:Glaive Lord/Challenges from Glaive Lord/@comment-4811344-20120726205358

Here are the rank unlocks for these Special Missions:

Stormin' Down the Bloons: Rank 35

Lightning Scar Special Ops: Rank 39

Alone in the Desert: Rank 45

BTD2 Expansion: Rank 49

Protect Monkey Castle: Rank 55

Elite Upgrades: Rank 59

Super Glue Return: Rank 65

Strapped for Upgrades: Rank 69

Trapped in the Lab: Rank 74

Return to the Lab: Rank 75