Heyo!
General
I always felt that Grave was lacking some form of better lategame performance or utility since with time he gets quite restricted in gamestyle. I tried to figure out a boost which does not benefit him too much in a sense of making him overpowered but still add a new form of playstile for GK. So the SotM can be an option in certain situation or if you have a spare Legacy, but he doesn't have to be boosted necessarily.
So my suggestion is to add a new way of using his ultimate in form a SotM-Ability in a more supportive way.
How does this look?
Curre