Aether or Chill Def

If it were me i think i would use him for Aether although chill def is hard to come by there are other skills you could use to substitute.

Chill Def. The only units that have the skill are Exalted Chrom (a 5* exclusive), Dancer!Ryoma (a seasonal), and Walhart (a limited unit).

Meanwhile, Chrom is in the 3* AND 4* pool, and feathers aren't really that difficult to obtain, even if you don't HM grind.

If you need said skills on one character why not inherit both? Just use regular Chrom and Walhart to pass down daylight sol for aether (i could be wrong about this one) and chill def 1 and 2, then use Exalted Chrom for both Aether and Chill def 3...

I agree with Deef, I do this all the time too, just usually without the 5 star exclusives. Also, if you have a spare 3* or 4* Raven lying around, use him instead and hold onto that Chrom for future fodder.