Fodder or Merge

Any mage or enemy phase unit that can use the extra attack will do, esp merge projects. Buf of course you want it on someone with already decent res so they can tank magic hits.

Think of it as fierce stance but with extra res for dragons and such.

Owl tomes tend to like bond skills, but atk/res bond is a bit unique because fast mages generally don't enjoy it as much as atk/spd bond. So it fits relatively well on an enemy phase mage with relatively high res to begin with, or enemy phase anti-mage daggers or bows with relatively low atk (ex: Felicia, Niles). However, even those characters tend to prefer atk/spd bond because mages can get so fast and getting hit twice can be quite dangerous unless you're using dull ranged and reach 40+ res. (but then are you using the QR seal? Probably someone else already uses it, so you're stuck with using gratia or green gift if you have a LA unit you want to get rid of).

Or just keep Lilina, why not, she looks lovely and this build works well on her with any IV (some better than others obviously, but even +def -atk or -spd this will work)
Green gift +res
Iceberg
Atk/res bond
QR
Atk ploy
Fortress res seal; she will have enough atk. Or res+ seal.

The C-skill and seal are flexible. Mages can have fun trying to get through 39+ res when their buffs get ignored. F.Morgan does a similar thing; her tome has the same effect, but she comes with mirror stance so it feels wasteful to me.

The other thing about atk/res bond is that you can plan a support partner specifically to aid the unit using it and use the spur you need.

Ex: Roy using steady breath close def build ally supported to neutral IV Innes (Nidhogg is like an owl tome)
Innes neutral IV
Nidhogg
Iceberg, glacies, or moonbow
atk/res bond
QR
spd ploy
Fortress res

Roy's C-skill is spur atk/spd or spur spd/res.

Notice that this time I did away with dull ranged. Innes has 34 base spd + 2 from his weapon + 3 from Roy's spur + 2 from ally support = 41 spd, and if it's not enough, we ploy the mage using 36 res. Fast mages don't have 36 res. The mage now has to fire into 45+ res: 31 base + fortress res + 5 from bond + 2 from weapon effect + 2 from ally support. They will not double without bowbreaker (which usually means a raven + TA mage which he won't KO without CA anyways), and Innes will double back for a win.