The Vulcan ambassador who mind-melds with Captain Picard is Sarek.
Sarek is a renowned Vulcan diplomat and the father of Spock. In the The Next Generation episode “Sarek,” he travels aboard the Enterprise-D for an important diplomatic conference with the Legarans. The crew soon notices an outbreak of irrational anger and emotional instability among themselves.
The cause is Bendii syndrome, a degenerative condition affecting elderly Vulcans. Sarek is losing control of the emotional discipline normally associated with Vulcans, and his telepathic feelings are radiating outward to people around him. To complete the negotiations, Sarek performs a mind meld with Picard, transferring the overwhelming emotions to him temporarily.
The experience gives Picard direct insight into Sarek's buried love, grief, and regret, including his feelings for Amanda, Spock, and his wife Perrin. Sarek later remains important to Picard because of the unusual bond created by that mind meld.