Crypto billionaire Sam Bankman -Fried has become a lender of last resort to his beleaguered industry. He may end up owning large chunks of it as well.

Mr. Bankman-Fried’s crypto exchange, FTX, is in talks to acquire a stake in BlockFi, a crypto lender that FTX gave a $250 million credit line this week, people familiar with the matter said. His other company, Alameda Research, also acquired a big ownership stake in Canadian crypto broker Voyager Digital Ltd.

Earlier this month, Alameda said it extended two credit lines, one for $200 million in cash and stablecoins, and another for 15,000 bitcoins, to Voyager.

Discussions between BlockFi and FTX are continuing, and no equity agreement has been reached, the people familiar said.

These agreements come after other high-profile investments by Mr. Bankman-Fried and his companies, and as crypto investors begin to sort through which firms will survive the current downturn.

Crypto firms have been grappling with a massive price slide that has erased $2 trillion in value since the market’s high in November. In early May, the stablesoin Terra USD collapsed, wiping out about $40 billion worth of crypto assets. A number of firms, including Celsius Network LLC and Three Arrows Capital Ltd., have come under severe liquidity constraints in recent months.

This week Voyager lowered the withdrawal limit for its customers to $10,000 over a 24-hour period, down from $25,000, according to an update to its website.

Voyager said Three Arrows owed it $666 million, and that Voyager was considering issuing a notice of default. Voyager lent the hedge fund 15,250 bitcoins and $350 million in USD Coin. Voyager had about $5.9 billion in cash and other assets on its balance sheet as of its most recent financial report in March. It reported $3.4 billion in crypto assets held and $2 billion in assets lent out.

Alameda acquired a $35 million stake in Voyager last month, paying $2.34 a share to acquire 14.96 million shares. On top of about 7.7 million shares owned by Alameda Ventures Ltd., it gave the combined entities, both of which are controlled by Mr. Bankman-Fried, an 11.56% stake in Voyager.

The purchase price was a discount of about 16% to the then-current market price, though it has lost value since then. On May 20, Voyager shares closed at $2.78. On Friday, Voyager shares were trading at 66 cents, down 9.6%. Year to date they are down 96%.

The discounted deal price isn’t all that unusual in the current environment, said H.C. Wainwright managing director Kevin Dede. "What you’ll see is a lot of private deals placed below market price," he said. "It depends on the financial condition of the company."

Some of Mr. Bankman-Fried’s other recent investments include a 7.6% stake in Robinhood Markets Inc. for $648 million, making him the trading app’s third-largest shareholder. In June, FTX acquired a Canadian crypto exchange called Bitvo for an undisclosed amount, and FTX’s U.S.-based division, FTX US, recently added brokerage-services firm Embed Financial Technologies Inc.

On Thursday, Alameda said it surrendered 4.5 million shares to Voyager, which were canceled by the company, lowering Alameda’s stake to 9.49%, with the result that it wouldn’t be classified as a reporting insider under Canadian securities laws. The shares were worth $2.6 million based on Wednesday’s prices. No money was exchanged in the cancellation.