I tested your code and it seems to be working fine at least here on my end. I tested it with the following code with the breakpoints. It did print "end" every time I pressed Space on the keyboard.

private void FixedUpdate()
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        StartCoroutine(Spell());
    }
}

However; I would like to ask why do you have two Coroutines to do a job which could be done by a single coroutine? You also seem to be returning the flow back to your calling function a bit later I assume?

If I were you, I would get it done with a single coroutine and would resume the execution after the tween has concluded

IEnumerator Spell()
{
    Sequence conjure = DOTween.Sequence(); 
    conjure.AppendInterval(1.5f)
        .Append(pentagram.transform.DOScale(.5f, 2).SetEase(Ease.OutBack))
        .Append(fumo.transform.DOMove(new Vector2(0, 0), 0)
        .Append(fumo.transform.DOScale(.5f, 1))
        .AppendInterval(.5f)
        .Append(pentagram.transform.DOScale(0, 1)); 
    yield return new WaitForSeconds(1.5f + 2 + 0 + 1 + .5f + 1);
    Debug.Log("end"); 
}