I had a wonderful fantasy book, which was part of a series, in the mid '90s. On the cover was a man that looked like Kratos from God of War. In the story, he at one point got a gem shoved into his chest by an old wizard that was giving him powers and glowing. WTF is this book? I can't find it ANYWHERE on the internet. HELP!
I haven't read the book you are referencing, but a bit of Googling points me towards the Dark Sun series.
One of the books in the series, The Crimson Legion, features a fairly God-of-War-esque character on the cover.
The Dark Sun series features a sword known as the Scourge of Rkard, so named because the sword (previously known just as the 'Scourge') was used to kill a character named Rkard.
There's no information I could find quickly about a character gaining powers by having a gem pressed into their chest, but that is a fairly common trope of the genre, so it seems possible.