The showdown with Morgana was a skirmish that occurred between Morgana and the Knights of Camelot on the Plains of Denaria.
Events
The battle began when a patrol led by Sir Leon encountered a hooded figure struggling to pull a cart through the Plains of Denaria. At Leon's order, the woman halted and told the knights that she was traveling to the Great Seas of Meredor. However, she refused to tell them what was in her cart and Leon motioned for his men to search it.
As they approached the cart, the woman turned and revealed herself to be the Lady Morgana. She used a stunning spell to send Sir Bertand flying, then proceeded to defeat the other three knights the same way. Leon and Elyan survived and returned to Camelot with news of Morgana's return, but Bertrand and Montague were killed outright (The Darkest Hour).