To upgrade BOB Control, you need to complete four prerequisites listed below: Gear Up 3 Buildings in the Home Village The first task is to gear up these three buildings: Cannon, Archer Tower, and Mortar. For this, you need a level seven Cannon in the Home Village and a level four Double Cannon in the Builder Base. Similarly, you'll need a level 10 Archer Tower in the Home Village and a level six Archer Tower in the Builder Base to gear up the Archer Tower. Lastly, you need a level eight Mortar in Home Village as well as a level 8 Multi Mortar in the Builder Base. Make sure to upgrade to Town Hall level 10 beforehand to ensure all these upgrades are possible. Upgrade Any Troop to Level 18 For this step, you first need to upgrade your Star Laboratory to level nine, and then choose which character you use the most and upgrade it to level 18. It is recommended, however, to upgrade either Baby Dragon or Power PEKKA for maximum efficiency, but it's really up to you to choose which troop to upgrade. Upgrade Any Builder Base Defense to Level 9 The quickest way to complete this step is to upgrade your Multi Mortar by spending 4.5 Million Builder Gold. In the past, players used to upgrade a wall to level nine as a workaround, but it doesn't work anymore. Upgrade the Battle Base Heroes to Level 45 Combined There are two Battle Base Heroes: Battle Machine and Battle Copter. The easiest way to achieve a combined level of 45 is by upgrading the Battle Machine to level 25, which will unlock the Battle Copter. The initial level of Battle Copter is 15, which means only five more upgrades would bring it to level 20 and complete this step. Upgrade the BOB Control and Unlock BOB's Hut As you complete each task, you can upgrade your BOB Control by level one until you reach level five and unlock BOB's Hut. After that, place the hut in the Home Village to get your 6th Builder in Clash of Clans. Buy Cheap Clash of Clans Gems at legit store MMOWOW.com , Clash of Clans Gems for Sale, instant delivery, safe transaction, 24/7 online customer support.