The foe has some ability to shrug off one type of damage, but conversely takes additional damage from another source. Choose one line from the following table.

The foe gains Resistance 2 to the selected damage type, Resistance 1 to its Complement, and Vulnerability 2 to its Opposition.

When you select this feature a second or third time, increase the Resistances (but not the Vulnerability) by +1 each. You may select this feature up to three times total, but cannot select it more times than the creature's level divided by two (rounded down).