Pinball FX3

You need to hit the red bumpers at the top right of the table. You must hit them about 15 times which can be tricky because there's no clear shot at the bumpers. You can either catch the ball with the right flipper when released then hit it immediately. You can also hit the ball up the blue right lane, so it drops onto the bumper, but don’t hit it too hard as it can go past them (this is a hard shot to make).

You'll know the fight is available when you hear the announcer says, "Expel the Invaders!". Now hit the ball up the orange/red Mordred ramp to enter the playfield.
Hit the lit up maces. Sometimes you need to knock the Knight out of the way to hit an invader. Use REWIND whenever you lose the ball, almost impossible to get this achievement without it!!!!

Video clip below of me hitting the bumpers the last few times times, then getting in there and winning the achievement - you have to hit a lot of the lit up maces/invaders pretty quickly or time runs out:

u av 2 hit the bumpers wiv a skillshot & then shoot up the right ramp when promted to get to the top of the Castle to shoot the Knights a few time & bamm cheevo shud pop... use rewind...