ReutersThe problems that emerged from Archegos Capital Management at the end of last week bled into Monday as a slew of huge banks saw their share rates decline.Heres how the $20 billion blowup unfolded.U.S. media stocks ViacomCBS and Discovery experienced extreme selling pressure on Friday, with each losing more than 27%. A couple of Chinese internet ADRs including Baidu, Tencent and Vipshop likewise suffered sell-offs of a similar magnitude last week.ADRs are American depositary receipts, essentially a certificate that represents a share of a foreign stock and is traded on American stock exchanges.The culprit for the massive selling was a required liquidation of positions held by the multibillion-dollar household office Archegos, CNBC reported.Archegos, founded by former Tiger Management equity expert Bill Hwang, had actually built huge positions in these stocks through swaps, a kind of derivative that financiers trade over-the-counter or among themselves without having to divulge the holdings publicly.These swaps generally involve higher-than-usual leverage.These large, leveraged bets came under pressure after ViacomCBS $3 billion stock offering through Morgan Stanley and JPMorgan earlier in the week broke down, which set off broad selling in the name.The initial weak point in ViacomCBS triggered a chain of events where the prime brokers rushed to exit the positions on Archegos behalf and resulted in an enormous margin call. The hedge fund was required to inject more money to cover the losses, amassing a forced liquidation of more than $20 billion.The sell-off in these names advanced Monday with ViacomCBS down more than 8%. Discovery was off by more than 3%.Significant losses A slew of big banks involved are warning of the fallout from the relax of specific trades however are not specifically discussing Archegos.Nomura, headquartered in Tokyo, provided a trading upgrade Monday pointing out a “significant loss” at one of its U.S. subsidiaries arising from deals with an unnamed U.S. customer. Japans largest investment bank stated it was examining the prospective extent of the loss, estimated at $2 billion. Its shares fell nearly 14% on Monday.Nomura did not instantly return a call from CNBC.Credit Suisse said it and a variety of other banks it didnt discuss were also impacted and had begun leaving positions with the unnamed company. The Zurich-based lenders shares were down more than 15% following the statement.”While at this time it is early to measure the specific size of the loss arising from this exit, it could be highly significant and product to our very first quarter results, notwithstanding the favorable trends revealed in our trading declaration earlier this month,” Credit Suisse said.It included that it would provide an additional update on the matter “in due course.”Goldman Sachs, Morgan Stanley, and Deutsche Bank likewise facilitated Archegos liquidation of its holdings in a number of the Chinese internet names through unregistered trades, CNBC reported.Deutsche Bank said Monday that it substantially de-risked its direct exposure connected with Archegos without sustaining any losses.”We are handling down the immaterial staying customer positions, on which we do not expect to sustain any loss,” the German lending institution stated in a statement Monday.Morgan Stanley also prevented substantial losses from the Archegos trades, sources informed CNBCs Leslie Picker.Goldman didnt immediately reply to CNBCs demand for comments.The Securities and Exchange Commission has actually been closely viewing the effect from Archegos margin call default. “We have been communicating and monitoring the situation with market participants since recently,” an SEC spokesperson said Monday– CNBCs Elliott Smith, Bob Pisani and Scott Wapner contributed reporting.