Inclusion Criteria:

          -  Participant must be 18 years of age inclusive or older, at the time of signing the
             informed consent.

          -  Participants must have histologically or cytologically confirmed diagnosis of Multiple
             Myeloma (MM), as defined by the IMWG.

          -  Participants having at least 3 prior lines of prior anti-myeloma treatments including
             an immunodilating agent (IMID) a proteasome inhibitor (PI) and an anti-CD38 monoclonal
             antibody.

          -  Participants with a history of autologous stem cell transplant are eligible for study
             participation when, transplant was >100 days prior to study enrolment and with no
             active infection(s).

          -  Participants with Eastern Cooperative Oncology Group (ECOG) performance status of 0-1,
             unless ECOG less than equal to (<=)2 is due solely to skeletal complications and/or
             skeletal pain due to MM.

          -  Participants with measurable disease defined as at least one of the following: Serum
             M-protein greater than equal to (>=)0.5 gram per deciliter (>=5 gram per liter) or
             Urine M-protein >=200 mg per 24 hours or Serum free light chain (FLC) assay: Involved
             FLC level >=10 mg per deciliter (>=100 mg per Liter) and an abnormal serum FLC ratio
             (<0.26 or >1.65).

        Exclusion Criteria:

          -  Participants with current corneal epithelial disease except mild punctate keratopathy.

          -  Participants with evidence of cardiovascular risk

          -  Participants with known immediate or delayed hypersensitivity reaction or idiosyncrasy
             to drugs chemically related to belantamab mafodotin or any of the components of the
             study treatment. History of severe hypersensitivity to other mAb.

          -  Participants with active infection requiring antibiotic, antiviral, or antifungal
             treatment.

          -  Participants with other monoclonal antibodies within 30 days or systemic anti-myeloma
             therapy within <14 days.

          -  Participants with prior radiotherapy within 2 weeks of start of study therapy.

          -  Participants with prior allogeneic transplant are prohibited.

          -  Participants who have received prior Chimeric Antigen T cell therapy (CAR-T) therapy
             with lymphodepletion with chemotherapy within 3 months of screening.

          -  Participants with any major surgery (other than bone-stabilizing surgery) within the
             last 30 days.

          -  Participants with prior treatment with an investigational agent within 14 days or 5
             half-lives of receiving the first dose of study drugs, whichever is shorter.

          -  Participants with >=grade 3 toxicity considered related to prior check-point
             inhibitors and that led to treatment discontinuation.

          -  Participants who have received transfusion of blood products within 2 weeks before the
             first dose of study drug.

          -  Participants must not receive live attenuated vaccines within 30 days prior to first
             dose of study treatment or whilst receiving belantamab mafodotin +- partner agent in
             any sub-study arm of the platform trial and for at least 70 days following last study
             treatment.

        Additional Exclusion Criteria for Sub-study 1 and Sub-study 2:

          -  Participants with autoimmune disease (current or history) or syndrome that required
             systemic treatment within the past 2 years.

          -  Exclusion for a recent (within the past 6 months) history of symptomatic pericarditis.

        Additional Exclusion Criteria for Sub-study 3:

          -  Participants with uncontrolled small and/or large intestinal disease.

          -  Participants with uncontrolled skin disease.

          -  Participants with any condition causing hypophosphatemia, hypokalemia or
             hypomagnesemia which is refractory to electrolyte replacement.

          -  Participants with previous administration of a gamma secretase inhibitor.

          -  Participants with concomitant administration of a strong or moderate CYP3A4 inhibitor
             or inducer.

        Additional Exclusion Criteria for Sub-study 4:

          -  Participant has an active autoimmune disease that has required systemic treatment in
             the past 2 years (i.e. with use of disease-modifying agents, corticosteroids, or
             immunosuppressive drugs).

          -  Participants who have received prior therapy with an anti-programmed death-1
             (anti-PD-1), anti-PD-1-ligand-1 (anti-PD-L1), or anti-PD-1 ligand-2 (anti-PD-L2)
             agent.

          -  Participant has a diagnosis of immunodeficiency or is receiving systemic steroid
             therapy or any other form of immunosuppressive therapy within 7 days prior to the
             first dose of study treatment. Use of inhaled steroids, local injection of steroids,
             and steroid eye drops are allowed.

        Additional Exclusion Criteria for Sub-study 5:

          -  Participants with Severe hypersensitivity to Isatuximab-irfc or to any of its
             excipients.

          -  Participants with prior treatment with other anti-CD38 monoclonal antibody within 6
             months of the first dose of study drug treatment.

          -  Participants with known intolerance or hypersensitivity to infused proteins products,
             sucrose, histidine, and polysorbate 80.