def METHOD_NAME(stage):
    """
    Args:
        stage (str): Stage name.
    Returns:
        Button: Entrance button
    """
    stage = stage.lower()
    if stage == 'tc1':
        return FROSTFALL_TC1
    if stage == 'tc2':
        return FROSTFALL_TC2
    if stage == 'tc3':
        return FROSTFALL_TC3
    if stage == 'sp':
        return FROSTFALL_SP
    if stage == 'ex':
        return FROSTFALL_EX
    raise CampaignNameError