Lock is a skill introduced in TD11: Starvader Invasion.
A unit that's locked is turned face down until the end of the player's (unit's player) turn and the unit / circle ceases to exist. Units that have been locked can not be use for attack, boost, intercept, Soul charge and they can not be
replaced with another unit or move to another circle.
Q&A
Q1. If I have a Alfred Liberator as my VG and 1 of my 5 RGs have been locked, will my VG's base attacks be
19000 or 21000 at Limit Break?
A1. 19000. Your Locked unit does not exist on the field anymore.
Q2. If my VG is Dragonic Overlord and I only have a Bahr which is Locked will my Dragonic Overlord gets POWER -2000?
A2. No. It will be treated as there are no unit on the RG circle, meaning skills that are/are similar to Lord are unaffected.
(Source for info on Lock: Freedomduo.)
List of units with lock: