Bonding is a new feature introduced in XCOM 2: War of the Chosen.
About Bonding Edit
Two soldiers can bond by increasing their cohesion level. This can be done simply by sending the soldiers out on combat or infiltration missions together. Cohesion is measured by a scale from 1.0 to 10.0, and once their cohesion level is at 10.0, the soldiers are eligible to be bonded. Every time the bond is leveled up, the scale resets, raising by 5 for each bond level (15 for 2, 20 for 3)
Bond Perks: Level 1Edit
At level 1 of a bond, both soldiers receive this :
Teamwork: Grant an extra action to the bondmate, while consuming one of your own. This has a single charge per mission shared between bondmates.
Bond Perks: Level 2Edit
At level 2 of a bond, the bondmates receive these three passives:
Covert Operators: When deployed on a Covert Action together, the duration of the operation is reduced by one day.
Stand By Me: Ending a move adjacent to a bondmate will cleanse any negative mental effects. This is a passive effect that is applied every time bondmates end a turn next to one another (diagonal squares don't count).
Spotter: Soldier is granted a +10% bonus to aim against targets that have attacked—or been attacked by—their bondmate. An additional +10% bonus to aim is granted if the bondmates are standing adjacent to one another.
Bond Perks: Level 3Edit
At the third and final level of a bond, the Teamwork ability is boosted, and they receive one final active ability:
Advanced Teamwork: Same as regular Teamwork, but with two charges instead of one.
Dual Strike: Bonded soldiers fire at a single enemy at the same time. This attack is a free action for the bondmate not using the ability.