Vow
Pledge, Oath, Covenant
noun, verbal noun
せいやく
誓い (ちかい) Vow, Oath
誓約 (せいやく) Vow, Pledge, Oath, Covenant
条件 (じょうけん) Condition, Conditions, Terms, Requirements
条約 (じょうやく) Treaty, Pact, Agreement
契約 (けいやく) Contract, Agreement
盟約 (めいやく) Pledge, Pact
約款 (やっかん) Agreement, Stipulation, Article, Clause
They say せい he makes his Yaks やく Pledge loyalty to him.