Eu3+-activated　red-emitting　inorganic　phosphors　have　been　favored　highly　for　their　classical　D-5(0)-＞　F-7(J)　(J　=　0,　1,　2,　3,　4)　emissions.　However,　the　fatal　drawbacks　of　poor　luminous　efficacy　and　weak　D-5(0)-＞　F-7(4)　transition　persist,　resulting　in　the　ongoing　challenge　of　achieving　far-red　emission.　This　research　reports　series　of　highly　efficient　far-red　phosphors　LnTeBO(5)　(Ln　=　La3+,　Y3+,　Gd3+):Eu3+　with　anomalously　strong　D-5(0)-＞　F-7(4)　transition,　resulting　from　the　distorted　square　antiprism　[Ln/EuO8].　Both　the　luminous　efficacy　and　thermal　stability　can　be　greatly　enhanced　via　the　simple　composition　variation.　[Ln/EuO8]　square　antiprism-triggered　D-5(0)-＞　F-7(2,4)　transitions　are　elucidated　in　depth,　acquiring　ultra-high　luminous　efficacy　(IQE　=　95%,　EQE　=　40%,　and　AE　=　42%)　and　near-zero　thermal　quenching　(99%@150　degrees　C　and　98%@200　degrees　C).　Subsequently,　the　versatile　utilizations　in　indoor　lighting,　plant　growth　lighting,　and　security　ink　are　illustrated.　This　finding　establishes　a　deep　understanding　for　constructing　high-quality　far-red　phosphors　via　the　Eu3+-centered　structural　units　of　square　antiprism.