80% shade is a tough area to plant up!
:
Here are some of my favourites.
For earlier colour try Bergenia, Primula, Epimedium and Pulmonaria. For later colour throughout the season try Ligularia's, Kirengeshoma, Aruncus, Chelone, Cimicifuga, Heuchera, Ferns and of course, Hosta. Be very careful of Convallaria (Lily-of-the-Valley) as it is a very aggressive spreader and can be terribly invasive.
There is a very lovely grass (pricey here) but well worth every penny. It is Hakonachloa macra 'Aureola'. Slow to establish but one of the most graceful and elegant of grasses. This grass looks amazing on mass lining a walkway and combined with ferns that are not aggressive. Yummy.
When using Hosta's, remember that one can stagger bloom period by choosing those that bloom early, mid and late season. Also use slug resistant types. Look for thick substanced and puckering leaves. Takes a hard working, starving slug to do much damage. Hosta 'Guacomole' has very fragrant flowers and the foliage is very bright and colourful when grown well.
Hosta 'Sum and Substance' is a huge specimen that will 'wow' anyone and it will tolerate sun as well.
I'm sure there's so much more but that's about all that's coming to mind at the moment.
Good Luck and enjoy.