A council exists for cross-domain conflict. Two functions want incompatible definitions of the same entity; a policy would cost one department a quarter's roadmap; a domain wants to expose data that another domain is regulated on. Those cannot be resolved inside a domain, and escalating each one to an executive committee does not scale. The council is the standing place where they are resolved, by the people accountable for the domains involved.
In practice. A council that works is small — the data owners, chaired by someone with executive weight — meets monthly, and works from a queue of specific decisions with a proposed answer attached. Minutes record what was decided and by whom, which is what makes it authority rather than discussion.
Where it goes wrong. The council becomes a status meeting. Twenty attendees, a deck, a round of updates, no decisions, and within two quarters the owners send delegates instead of attending. The reliable test: if the agenda does not contain the word "approve", cancel the meeting and write an email.