Sullivan & Cromwell and Cravath Swaine & Moore are among the law firms to have secured lucrative roles on AT&T's $85.4bn (£70bn) takeover of Time Warner, a deal whose value reaches $108.7bn (£89bn) when accounting for the US media giant's net debt.

The cash and stock sale is set to create a company for the new media age, in which telecoms providers have scooped up original content providers in order to compete with technology giants pushing into streaming services.

AT&T has turned to Sullivan & Cromwell and Arnold & Porter to advise on the deal. Both firms advised AT&T two years ago on the company's $48.5bn (£40bn) purchase of satellite TV company DirecTV. Sullivan is fielding a team of lawyers spread across its New York, Los Angeles and Palo Alto offices, led by M&A managing partner Joseph Frumkin and corporate partners Eric Krautheimer and Melissa Sawyer.

Cravath is advising Time Warner, the owner of TV channels including CNN and HBO, on the landmark transaction. Faiza Saeed, who earlier this year was named the firm's first female presiding partner, is leading a team alongside fellow M&A partner Eric Schiele and antitrust partner Christine Varney.

Weil Gotshal & Manges has also taken a role on the deal, advising AT&T's financial advisers, JP Morgan and Perella Weinberg, with a New York team led by corporate partners Michael Aiello and Matthew Gilroy, alongside banking partner Morgan Bale.

Cravath's relationship with Time Warner and its predecessors goes back nearly a century. Former Cravath presiding partner Maurice 'Tex' Moore, who died 30 years ago, first took on the company as a client as a favour to his brother-in-law – future magazine magnate Henry Luce, the founder of Time and Fortune.

Former Cravath partner Robert Joffe, who died in 2010, helped create the current iteration of Time Warner by advising what was Time Inc on its $15.2bn (£12.4bn) merger in 1989 with Warner Communications. In 1996, Cravath represented Time Warner on its $7.5bn (£6.1bn) merger with Turner Broadcasting System and four years later, Cravath took the lead for Time Warner on its ill-fated $182bn (£149bn) union with AOL. Cravath famously received a $35m (£29m) success fee from Time Warner for its work on the AOL merger, which the firm ultimately helped dissolve in 2009.

The dissolution of that deal heralded a new era, one in which Cravath would advise Time Warner on a series of divestitures, such as the $537.5m (£440m) sale of its books group to France's Lagardere in 2006 and its $9.25bn (£7.6bn) separation two years later from Time Warner Cable. In 2013, Cravath handled Time Warner's spin-off of its publishing unit, and the following year the firm again took the lead for the company in rejecting an $80bn (£65bn) takeover offer from 21st Century Fox.

Former Kirkland & Ellis litigation partner Paul Cappuccio has served as Time Warner's general counsel since the completion of its merger with AOL. AT&T's general counsel is former Haynes and Boone partner David McAtee, who took up the role a year ago.