To go over an axle end cap that otherwise cannot come off, internal cassette lockring style
I've got a superstar tool which looks remarkably like this lifeline one which has never yet failed to go over an end cap
https://www.wiggle.com/p/lifeline-cassette-and-fork-top-cap-tool
I’ve used the Shimano one always without removing the end cap. TL-LR15
I think the last few times this question has been asked the answer was Icetoolz. https://www.icetoolz.eu/en/icetoolz-cassette-lockring-tool-shimano-09c3/a5561
Worked for me, anyway.
Surely this is exactly what externally splined lock rings are for? Is it to remove a badly specified one?
That icetoolz one looks quite deep (deeper than my Shimano one anyway ) so I would give that a shot…
&£@?!! Well that’s a bugger. Hammer, pointy drift and abuse some of that shimano branding?