NiGHTS Into Dreams - https://www.sega60th.com/register
On the registration screen, you need to pick "Steam" as you preferred system and then log in to your account and give permission--at this point, Nights Into Dreams will be added to your account.
Free for limited time, Sonic The Hedgehog 2 - https://store.steampowered.com/app/7116 ... edgehog_2/
Also three freebie games will each release a day apart:
Endless Zone - Oct 16 https://store.steampowered.com/app/1368 ... less_Zone/
shooter homage to Fantasy Zone features 3D visuals that are a far cry from Fantasy Zone's gorgeous visual style, but as a mash-up starring the Opbot from Endless Legend
Streets Of Kamurocho - Oct 17 https://store.steampowered.com/app/1368 ... Kamurocho/
A Yakuza/Streets of Rage 2 mash-up where you play as Kiryu and Majima, and brawl your way through various thugs. It's got a lovely chunky pixel art style, and while it doesn't feature any blood, you can pick up weapons around each level and beat your enemies up with them.
Golden Axed: A Cancelled Prototype - Oct 18 https://store.steampowered.com/app/1368 ... Prototype/
A real Golden Axe follow-up prototype, which was in the works at Sega Studios Australia before it was shuttered in 2013. As you can see from the trailer below, it didn't get very far along in development, although the environments look quite nice. It also supports up to four players, although you'll only have one day to play it.