On NA only OG Cu and Herc have received grails but once most of my servants are maxed I’ll raise Ecchan (MHXA) and Kiara to level 100.
In the future I’m planning on grailing Murasaki to 100 and Kagetora to 90.
Not sure who else I’ll use them on, I’ve indulged in extravagancy on my JP account so I’m not in a rush for NA.
I’m a bit tempted to raise Serenity to level 80 but I’m pretty sure I’ll use Shiki a lot after I get her next year.
I’ll raise her skills a bit more and experiment before I decide.
For the most part it is simply that I like using them and that they are useful is a bonus.
Ecchan’s character convinced me to get her and give her some grails. She might be a bit awkward but I like how she works in battle.
Kiara is fun to play around with and meshes well with my preferred arts teams.
Murasaki is odd but really entertaining to use and while she isn’t a master of anything she does provide lots of utility. The kimono also took care of what I found an unappealing design.
Kagetora is great in all aspects, design, voice, skills, animations and is a rare Arts based ST lancer.