As long as it remains reasonably moist, Tricyrtis is the first thing that springs to mind.

Alchemilla mollis is just about the easiest, and it also seeds itself so you get more for free. Lots of perennial geraniums would fill the bill - Johnson's Blue grows happily in shade for me. Lamium maculatum is very easy and low growing and flowers for a long time. Dicentra eximea or formosa will grow in shade and have pretty pink or white bells shaped flowers not more than a foot tall, and ferny leaves. For summer colour you could add some fibrous rooted begonias, but they would need replacing every year. There are several variegated euonymus fortunii - small evergreen shrubs that can readily be trimmed to the size and shape you want with just a light annual pruning - the variety emerald 'n gold is particularly bright and cheerful.All these are very easy and reliable.

Epimediums would be my first choice - Robust, low to zero maintenance, mostly evergreen and with year-round interest so the site won't revert to bare soil every winter. I have a pics of a number of varieties in my profile - photos on here.