Warhammer 40,000: Inquisitor - Martyr

Firstly you need to reach level 20 with your battle sister to unlock you 1st banner type, the banner of valor. Different banner types will unlock at varying levels after that.

Then you need a banner to drop from enemies or chests in a mission. I was getting 1 or 2 a mission as drops.

Equip the banner to your belt slot, replacing grenades, shields etc. You deploy the banner by pressing . Banners only last for a short time. You only have a certain amount of charges available, you can resuply more in crates dotted around missions. Each banner has random skill sets that come with it to help your sister. There’s a cooldown timer after each use.

Deploy it 150 times to unlock the Achievement. You can track your progress percentage in Achievement tracking through the guide button.

You can spend passive skill points on upgrading banners, there’s a few upgrades for lowering cooldown times.

There’s also a perk available in the character section of the menu called Utility Harness, this gives you 2 extra charges to start with and 1 more charge resupplied from crates.

Occasionally banners will appear in the store.

If you stand in the banner range when deployed, a coloured circular area around the banner. You can work on the Achievement for killing 500 enemies whilst within the banner range, best done with a ranged weapon.

Good luck with the Achievement.