あらんことを

may there be; may ... happen

→ 有る

phrase Common #6,777

may there be; may ... happen A literary, archaic-sounding expression used in wishes, often after a noun such as 幸 (happiness or good fortune). あらん is an old volitional form of ある.

JA: 皆さんに幸あらんことを。

EN: May good fortune be with you all.

祝福のあらんことを

May blessings be upon you.

— ロード・オブ・ザ・リング／王の帰還 (2003)