I attached "Crown of winter" to my character.

So the character gains immune to character ability.

When facing cards like "House Manderly Escort", is that mean the "+1 STR" of this card has no effect?

I am a bit confuse of the extent of "immune to character ability & immune to event"

Thanks

Crown of Winter's immunity only applies to opponent's character abilities and events. So, if you have attached the Crown to a character that either has or gains the House Manderly trait, the character would still benefit from the strength bump.

"Immune to character abilities" means that the immune card ignores all character abilities that try to directly change or affect it. That includes favorable or beneficial abilities as well. So sure, Crown of Winter stops your opponent from using Castellan of the Rock from kneeling the character, but it also stops you from using Mors Umber to increase its STR.

That said, a character can never be immune it it's own ability - so immunity wouldn't stop Wyla Manderly from giving herself +3.

And, since immunity to character abilities only works to block effects that would be applied to the immune card, putting Crown of Winter on Wyla or Wyman Manderly doesn't do anything to House Manderly Escort (their immunity doesn't stop them from counting as a "House Manderly character you control").

Check out the FAQ for a complete breakdown on immunity and the scope of immunity.