on an apportionment of costs, both the apportionment of costs and the fixing of costs to be apportioned are dealt with in a single decision. Transfer of opponent status The opponent status cannot be freely transferred. As far as legal persons are concerned, the opposition can only be transferred or assigned to a third party together with the business assets belonging to a company, i.e. its economic activity, and more precisely the assets in the interests of which the opposition was filed. However, the status of an opponent passes to, i.e. is transmitted to, the opponent's universal successor in law in the case of a universal succession, such as for example in the case of a merger of two companies. Intervention and observations by third parties Intervention under Article 105 EPC Under , any third party may intervene in ongoing opposition proceedings after the 9-month opposition period has expired, if the third party proves that "(a) proceedings for infringement of the same patent have been instituted against him, or (b) following a request of the proprietor of the patent to cease alleged infringement, the third party has instituted proceedings for a ruling that he is not infringing the patent." In other words, a third party may intervene "if faced with an infringement action or allegation of infringement (...) instituted in a national jurisdiction under national law." The admissibility of an intervention is subject to conditions. The so-called notice of intervention must inter alia be filed within three months of the date on which proceedings referred to in Article 105 are instituted. An admissible intervention is treated as an opposition. If the intervention is admissible, the intervener becomes party to the opposition proceedings. An intervention may be based on any ground for opposition under Article 100 EPC, and the intervener may also introduce new facts and arguments, which can therefore not be regarded as late filed. The possibility to intervene not only exists during pending opposition proceedings before an Opposition Division (i.e., during the first instance proceedings), but also during subsequent pending appeal proceedings before a Board of Appeal (i.e., during the second instance proceedings). An intervener who intervened during appeal proceedings is, however, not treated as appellant, but merely as party as of right within the meaning of . This has the consequence that, if the sole appellant withdraws their appeal, the appeal cannot continue with only an intervener who