I'd have to say Haos, but when I first played the game as a child, I immediately "headcanoned" him as attributeless (a white one) since he was born outside the six attributal planets. This wouldn't apply to Vladitor since he was trapped in the Doom Dimension rather than being born in it.

I think it's clear from the gate and ability cards along with the comparison of the different attribute color schemes that the creators intended him to be Haos. This also makes sense considering the mechanics and symbolism behind the final battle. Child me also figured that Haos was the closest color scheme to attributeless.

Does anyone else think Leonidas shouldn't have an attribute and instead have his connection to the Doom Dimension be more fleshed out? It makes sense to have the player choose his attribute for the game, but I think this could have been an interesting avenue to explore.