Max - which has seen its share price on a strong upward trend throughout this year - has enlisted Endeavour to help with finances required by Colombia's National Mining Agency.
In return, Endeavour will take a smelter-royalties return and 5% ownership of Max.
Endeavours' net smelter returns royalty will be an underlying 0.5% and cover new mineral tenures, but not the ones that Max currently has.
And Endeavour has subscribed for 6.6 million units of Max's currently oversubscribed private placement, which should result in Endeavour owning about 5% of Max's issued and outstanding shares after the private placement closes.
Endeavour Silver CEO Dan Dickson said the company believes the Cesar project may be the world's largest undeveloped copper-silver district.
Max pointed to Cesar's credentials, including: its location at the northern portion of the world's largest producing copper belt, the Andean; nearby mining giants Glencore and Chevron; and proximity to critical infrastructure.
Max CEO Brett Matich said the company was drawn to Endeavour's financial and technical expertise.
"This partnership will significantly enhance Max's goal of delivering long-term value to Max shareholders," Matich said.
Max's share price has steadily grown from C$0.185 (US$0.15) in mid-December to C$0.445 as of March 21. The company had a market capitalisation of C$45.34 million.
Endeavour Silver, meanwhile, was quoted on the TSX at C$6.22/share on March 21, having risen 3% day-on-day. The company had a market capitalisation of C$1.12 billion.