Later, with Thor banished and Odin fallen into his Odinsleep, Loki placed himself on the throne as regent and demanded Heimdall's loyalty. Although he grudgingly accepted, Heimdall opted to only observe a literal interpretation of his vow to Loki and did not interfere when Sif and the Warriors Three used the Bifrost to reach Thor. Enraged, Loki dismissed Heimdall as a subject, thus releasing the protector of the Bifrost from his vow. Heimdall responded with an immediate attack, but Loki simply froze him in a block of ice before the blow could strike.
Heimdall was the all-seeing and all-hearing Asgardian and former guard of the Bifrost Bridge . He could see and hear nearly everything that happens in the Nine Realms . Despite vowing to obey the orders of Odin , Heimdall was prepared to commit treason if it meant protecting the Realms, as he allowed the Warriors Three to return Thor from Midgard to defeat Loki .