Thread:MasterAdventZero/@comment-14250-20191127233349/@comment-12642484-20191129094107

Warp Portal is magic, since it uses a magic circle. It requires both starting point and destination to have such a magic circle, as well as a catalyst (a ring in Rimuru's case) to work. After Rimuru gained the Extra Skill Spatial Travel he no longer needed the catalyst for that and once memorizing the spatial coordinates (or the destination being in range of his Magic Sense) he can directly use Spatial Travel to get there instead, not needing Warp Portal for that anymore.