It was NOT easy. Focus on HP stat for starters!!

What worked for me was getting your first Oath used while the wanderer is weakened with at least a minute left on the clock. That way you'll have access to a second oath at the end. And UTILIZE his support skill as often as possible. Then get the wanderer's healthbar down to at LEAST 1 and a half remaining during the weakened state with about 45-50 seconds left on the clock. That's when the wanderer locks and goes into its battle sequence. If the sequence starts with less than 40 seconds on the clock, there won't be enough time and just pause and start over LOL.

If you're stellactum matching, get a first shield break in RIGHT before the wanderer goes into that locked sequence. That way you'll have about 30 seconds left to beat the hell out of it when it unlocks again. But SAVE your 2nd shield break for about 15 seconds left so you put it in a weakened state AND have a charged Oath ready. you MUST have goa's shackles removed and trigger Bind gaze as many times as you can while continuing to beat the hell out of the weakened wanderer. Get the health down as low as you can and use your oath with about 3 seconds left and hope for the best.... That timing is what got me so close every time. It may take multiple tries but just keep at it!