Mimerkki, metsän emäntä, metsän armas antimuori,
siniviitta viian eukko, punasukka suon emäntä...
- Kalevala, XIV
Mielikki (also called Mimerkki) is an ancient Finnish goddess, the queen of the forest. Her husband is Tapio, the ruler of the forests. They have son Nyyrikki and daughters Tuulikki and Tellervo.
One of her most interesting appearances was in the 14th poem of Kalevala. Lemminkäinen, in order to marry Louhi's daughter, was tasked by this coldish empress of North to go skiing around and hunt the Elk from Hell (or is it the Moose of Doom? The translations are pain =). After noting the task was somewhat difficult that he thought, he went to the hall of Tapio. Seeing Mielikki and Tellervo wearing ragged and ordinary clothes (a sign of bad hunting luck!), he was wondering why they were clothed so, considering they usually appeared in fabulous clothes¹, adorned with pearls and gold (which would obviously be a better omen). Using the traditional weapon of mass distraction favored by the epic heroes, the Endless Poetry, he gained the favor of Mielikki, and was thus able to catch the alcine mythical beast.
Mielikki was also the goddess to whom the hunters in general prayed for hunting luck (just like Lemminkäinen). Also, when the wives sent the herd to the pastures, they prayed Mielikki's protection (as does Ilmarinen's wife in 32nd poem when she sends Kullervo to herd the cattle).
¹ ...fabulous, even though the above snippet says "Blue cloak (...) red socks." No comment...
Okay, Christianity came to Finland to stay, the old gods and heroes saw it better to move away (though Väinämöinen said he'll stop by later if he has time), and they made some very interesting contracts with RPG makers and fantasy fiction writers in USA.
And so, Mielikki has found her way to Forgotten Realms, and has not changed that much.
Before she noted that in the FR pantheon the Marketing Department is in the Netherworld and should as such be despised, she agreed to get a symbol and appearance change for higher "profits", whatever those are. So unicorn it is...
She's an intermediate forest goddess (of neutral good alignment), allied with to Silvanus and other deities of forestlands. One of her most famed worshippers is Drizzt Do'Urden.