Bootstrap4 Accordion: how to style accordion's borders using SCSS

Question

as you can see the question is simple: I cannot manage to style correctly an accordion's borders using scss, at least not entirely. My idea is to use a border-image to customize more my accordion. I'll show you my html and scss. Thanks in advance guys! I can't understand why I get white borders and my edited ones attached together in the same place?! My best result I can get is when adding border-left: none; border-right: none; inside .accordion .card ( second picture ).

#myAccordion{
    margin-top: 15%;
    border: none;
}

.accordion .card{
    border-image: url(../assets/background_assets/hr-edited.png) 100 stretch;
    border-image-width: 10px;
}
.accordion .card .card-header{
    background-color: #252525;
    border: none;
}
.accordion .card .card-body{
    color: #fff;
    background-color: #1A1B1D;
    border: none;
}

<!-- Start Accordion -->

        <div class="accordion col-12 col-md-8" id="myAccordion">
          <div class="card">
            <div class="card-header" id="headingOne">
              <h5 class="mb-0">
                <button class="btn btn-link" type="button" data-toggle="collapse" data-            target="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
                  Steinur Goldbrewer
                </button>
              </h5>
            </div>
        
            <div id="collapseOne" class="collapse show" aria-labelledby="headingOne" data-parent="#myAccordion">
              <div class="card-body">
                Dopo la fuga Steinur divenne un’altra persona: dipendente dall’alcol, burbero ed egoista, avido di monete. 
                Il suo unico scopo è un desiderio di vendetta che si è radicato così in profondità che alcuni potrebbero ritenerlo malvagio e spietato. 
                La maggior parte delle volte è sbronzo e poco lucido ma quando sente odore di combattimento si lancia a testa bassa e sferra colpi micidiali con violenza incredibile 
                come se stesse picconando vene di ferro nelle profondità di una montagna.
              </div>
            </div>
          </div>
          <div class="card">
            <div class="card-header" id="headingTwo">
              <h5 class="mb-0">
                <button class="btn btn-link collapsed" type="button" data-toggle="collapse" data-target="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
                  Character #2
                </button>
              </h5>
            </div>
            <div id="collapseTwo" class="collapse" aria-labelledby="headingTwo" data-parent="#myAccordion">
              <div class="card-body">
                Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
              </div>
            </div>
          </div>
          <div class="card">
            <div class="card-header" id="headingThree">
              <h5 class="mb-0">
                <button class="btn btn-link collapsed" type="button" data-toggle="collapse" data-target="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
                  Character #3
                </button>
              </h5>
            </div>
            <div id="collapseThree" class="collapse" aria-labelledby="headingThree" data-parent="#myAccordion">
              <div class="card-body">
                Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
              </div>
            </div>
          </div>
          <div class="card">
            <div class="card-header" id="headingFour">
              <h5 class="mb-0">
                <button class="btn btn-link collapsed" type="button" data-toggle="collapse" data-target="#collapseFour" aria-expanded="false" aria-controls="collapseFour">
                  Character #4
                </button>
              </h5>
            </div>
            <div id="collapseFour" class="collapse" aria-labelledby="headingFour" data-parent="#myAccordion">
              <div class="card-body">
                Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
              </div>
            </div>
          </div>
          <div class="card">
            <div class="card-header" id="headingFive">
              <h5 class="mb-0">
                <button class="btn btn-link collapsed" type="button" data-toggle="collapse" data-target="#collapseFive" aria-expanded="false" aria-controls="collapseFive">
                  Character #5
                </button>
              </h5>
            </div>
            <div id="collapseFive" class="collapse" aria-labelledby="headingFive" data-parent="#myAccordion">
              <div class="card-body">
                Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
              </div>
            </div>
          </div>
          <div class="card">
            <div class="card-header" id="headingSix">
              <h5 class="mb-0">
                <button class="btn btn-link collapsed" type="button" data-toggle="collapse" data-target="#collapseSix" aria-expanded="false" aria-controls="collapseSix">
                  Character #4
                </button>
              </h5>
            </div>
            <div id="collapseSix" class="collapse" aria-labelledby="headingSix" data-parent="#myAccordion">
              <div class="card-body">
                Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
              </div>
            </div>
          </div>
          

        </div> <!-- End Accordion -->

Answer 1

The border styling is from the .card element.

https://codepen.io/cwerner/pen/JjZvZKj

Tip: wrap the accordion in a class in your scss - unless you want all the .cards to inherit the border styling ofc..

.custom-class {
  .card {
    border: 1px solid orange;
  }
}

Hope this helps?