How to gain attunement slots with warrior? - Dark Souls
For Dark Souls on the Xbox 360, a GameFAQs message board topic titled "How to gain attunement slots with warrior?".
Attunement (Dark Souls III)
Attunement Slots are the player's maximum equipped number of , and . Attunement slots are based on Attunement, at level 10 Attunement the player gains his first Attunement Slot.
Attunement | Dark Souls 3 Wiki
It can have been more akin to DS2 or even DS3's variation of Attunement albeit slightly toned down to fit original Dark Souls 1 design (considering in DS2 Attunement also increased casting speed).