A Study to Investigate the Safety and Efficacy of Belantamab for the Treatment of Multiple Myeloma When Used as Monotherapy and in Combination Treatments

Inclusion criteria * Participants at the time of signing the Informed Consent Form (ICF) are at least 18 years old or are of the legal age of consent in the jurisdiction in which the study is taking place. * Participants who have histologically or cytologically confirmed diagnosis of Multiple Myeloma (MM), as defined by the international myeloma working group (IMWG) and have progressed on or following the last line of treatment * Part 1 and Part 2: Participants who have received at least 3 prior lines of anti-myeloma treatments, including any immunomodulatory drug (IMiDs lenalidomide, pomalidomide or thalidomide), a proteasome inhibitor, and an anti-CD38 monoclonal antibodies (mAb) (either in combination or separately). * Part 3: Have received at least 1 prior line of treatment anti-myeloma treatments, including lenalidomide. Prior anti-CD38-containing regimen is not mandated, however no more than 70% of participants recruited may be anti-CD38 naïve. * Participants with a history of Autologous stem cell transplant (ASCT) are eligible for study participation provided the following eligibility criteria are met: * transplant was greater than (\>)100 days prior to screening. * No active bacterial, viral, or fungal infection(s) present * Eastern cooperative oncology group-performance status (ECOG-PS) of 0 to 2. * Measurable disease defined as at least ONE of the following: * Serum M-protein concentration greater than or equal to (\>=) 0.5 gram (g)/ deciliter (dL) (\>=5 gram/liter \[g/L\]) * Urine M-protein excretion \>=200 milligram (mg)/24 hours (\>=0.2 g/24 hours) * Serum free light chain (FLC) assay: involved FLC level \>=10 mg/dL (\>=100 milligrams per liter \[mg/L\]) and an abnormal serum FLC ratio (less than \[\<\]0.26 or \>1.65) * Have adequate organ system function as defined by the laboratory assessments * All prior treatment-related toxicities (defined by National Cancer Institute-Common Toxicity Criteria for Adverse Events \[NCI-CTCAE\], v5.0, 2017) must be Grade less than or equal to (\<=)1 at the time of screening except for alopecia (any grade), neuropathy (Grade \<=2), or endocrinopathy managed with replacement therapy (any grade). * Participants or legally authorized representative (LAR) (if applicable per local regulation) capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the ICF and in this protocol. * Male Participants (for parts 1b, 2 and 3): * Contraceptive use by men should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. Male Participants enrolled in part 1 (and expansion) cohort receiving belantamab monotherapy are not required to use contraception * Male participants are eligible to participate in parts 2 and 3 if they agree to the following during the intervention period and for at least 6 months after the last dose of study intervention to allow for clearance of any altered sperm: * Refrain from donating fresh unwashed semen PLUS either: * Be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent OR * Must agree to use contraception/barrier as detailed below * Agree to use a male condom, even if they have undergone a successful vasectomy, and female partner to use an additional highly effective contraceptive method with a failure rate of \<1 percent (%) per year when having sexual intercourse with POCBP who is not currently pregnant. Male participants should also use a condom when having sexual intercourse with pregnant females. * A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: * Is NOT a Participant of child-bearing potential (POCBP) or * Is a POCBP and using a contraceptive method that is highly effective (with a failure rate of \<1% per year), preferably with low user dependency, 30 days prior to treatment start, during the intervention period and for 4 months after the last dose of study intervention and agrees not to donate eggs (ova, oocytes) for the purpose of reproduction during this period. The investigator should evaluate the effectiveness of the contraceptive method in relationship to the first dose of study intervention. * Part 3: Due to pomalidomide being a thalidomide analogue with a risk for embryofetal toxicity and prescribed under a pregnancy prevention/controlled distribution program, POCBP will be eligible if they commit either to abstain continuously from heterosexual sexual intercourse or use two methods of reliable birth control (one method that is highly effective plus an additional barrier method), beginning at least 4 weeks prior to initiating treatment with pomalidomide, during therapy, during dose interruptions and continuing for at least 4 weeks following discontinuation of pomalidomide treatment. Thereafter, POCBP must use one contraceptive method that is highly effective (with a failure rate of less than (\<)1% per year) for a further 3 months (total 4 months). * The investigator should evaluate the effectiveness of the contraceptive method in relationship to the first dose of study intervention * All POCBP must agree not to donate eggs (ova, oocytes) for the purpose of reproduction during this period. Exclusion criteria * Diagnosis of primary Amyloid Light chain (AL) Amyloidosis, active Polyneuropathy, organomegaly, endocrinopathy, myeloma protein, and skin changes (POEMS) syndrome, primary plasma cell leukemia. * Part 3: Active or history of venous or arterial thromboembolism within the past 3 months. Contraindications to or unwilling to undergo protocol-required anti-thrombotic prophylaxis * Any serious and/or unstable pre-existing medical, psychiatric disorder, or other conditions (including lab abnormalities) that could interfere with participant's safety, obta