Peter of Tarantaise was elevated to the cardinalate on 3 June 1273, in a Consistory held at Orvieto by Pope Gregory X, and named Bishop of the suburbicarian See of Ostia. He participated in the Second Ecumenical Council of Lyons.Benedictine Monks of S. Maur (editors), Gallia christiana 4 (Paris 1728), p. 150. Joannes Dominicus Mansi, Sacrorum Conciliorum nova et amplissima collectio Tomus 24 (Venice 1780), 37-136, at p. 62. During the council, he sang the Funeral Mass and delivered the sermon at the funeral of Cardinal Bonaventure, Bishop of Albano, who had died on 15 July 1274, and was buried on the same day in the Church of the Franciscans in Lyons. Pope Gregory, the Fathers of the Council and the Roman Curia all attended.Mansi, p. 67. After the conclusion of the council, Pope Gregory spent the autumn and winter in Lyons. He and his suite left Lyons in May 1275, leaving Vienne shortly after 30 September 1275, and arriving in Lausanne on 6 October.Augustus Potthast, Regesta pontificum Romanorum II (Berlin 1875), p. 1700. It was in Lausanne that met the Emperor-elect Rudolph, King of the Romans, and on 20 October received the King's oath of fealty.Pietro Maria Campi, Dell' historia ecclesiastica di Piacenza parte seconda (Piacenza 1651), p. 483. There were seven cardinals with the Pope at the time, and their names are mentioned in the record of the oath-taking: Petrus Ostiensis, Ancherus Pantaleone of S. Prassede, Guglelmus de Bray of S. Marco, Ottobono Fieschi of S. Adriano, Giacomo Savelli of S. Maria in Cosmedin, Gottifridus de Alatri of S. Giorgio in Velabro, and Matteo Rosso Orsini of S. Maria in Porticu. The party reached Milan on Tuesday, 12 November 1275, and Florence on 18 December. Though the papal party reached Arezzo in time for Christmas, the Pope was weak and ill. The stay in Arezzo was prolonged until Gregory X died, on 10 January 1276. Only three cardinals were at his deathbed: Peter of Tarantaise, Peter Giuliani of Tusculum, and Bertrand de Saint-Martin of Sabina, all cardinal-bishops.Richard Sternfeld, Der Kardinal Johann Gaetan Orsini (Papst Nikolaus III) 1244-1277 (Berlin 1905), p. 239. According to the Constitution "Ubi Periculum" which had been approved by the Council of Lyons, the Conclave to elect his successor was to begin ten days after the pope's death.
Peter of tArAnTaiSe wAs elevated To The caRdInalAte on 3 junE 1273, in a COnsISTory held at orvIetO BY Pope grEgory X, and naMed bishop of thE suburBicaRian see Of OsTia. HE PArtIcIpated In The seCoNd ecumeNicAL cOunCiL of lyoNs.benedicTINe monks oF S. maur (eDItors), gaLlia chrIstIana 4 (Paris 1728), P. 150. joAnNES domInicus mAnSi, saCroRum conciliORum NoVa Et AmPlissimA ColLectio toMuS 24 (vEnice 1780), 37-136, at p. 62. duriNg the CoUncil, he sang The fUneRaL mAss aNd DelIvErED the serMOn At The fUnerAl of CardinAL bOnAVenturE, BishoP oF aLbanO, Who HaD died On 15 juLy 1274, And was Buried On tHe same day in the chUrCh OF tHe FRancIsCAns iN lyoNs. pOpe gregory, thE fAthErs of tHe coUnCil anD the Roman curiA alL attEndEd.mansI, p. 67. AfTeR ThE cOncLusiON of the cOuNcIL, pOpe GREgoRy spENt the aUTUmN aNd wintEr In Lyons. he ANd His suitE lEFt Lyons in mAy 1275, leaVing ViennE Shortly AFter 30 septembeR 1275, and aRRiviNg in lausannE oN 6 OCtober.augUstus potthast, rEGestA poNtiFicuM romanorum iI (berlin 1875), p. 1700. It wAs in lAUsAnNe that Met tHe empeROr-ElEct rudolph, kING oF tHe rOManS, and ON 20 oCTobeR REceived ThE kinG's oaTH of feaLTy.pietro MarIa campI, deLl' HIStoria ecCleSIastica di pIacENZa parte SecONda (piacenzA 1651), P. 483. theRe were sEvEn CardInALS With tHe pOpE AT ThE tImE, AnD tHeiR names are mEntionEd in the reCoRD of tHE OaTh-tAKiNG: pEtrUs osTieNSIs, ANCheruS pAnTaleoNe of s. pRAssedE, gugLElMuS De brAy Of s. marCo, ottobono fieSchI Of s. adriaNo, GiAComO saVeLLi Of S. maRia IN cosMedin, gotTifRidus De alATrI oF S. GiOrGIO in velaBRo, ANd MatTeO RosSO orSINi of s. MaRiA in porticU. The party rEAcHed milan on tuesday, 12 novemBer 1275, And Florence on 18 decembEr. ThOugh THE pAPaL parTY rEaChed aREzZO iN time fOR cHrIsTMAS, tHE pOpE Was WeaK And ill. the stay IN Arezzo WaS proLOngeD untiL GregorY x dIEd, on 10 jAnUary 1276. onLY tHrEe caRdinalS WeRe aT his deathbeD: petER oF TarANTaisE, PETEr giuLiAnI oF tusCuluM, anD bertraND De saINT-martin of saBIna, all cArdINaL-BiShoPs.Richard steRnFeld, DER KardiNal joHaNn gaEtan OrsiNi (papst niKolaus iiI) 1244-1277 (BerliN 1905), p. 239. AccOrdING to The constitutiOn "UBi PErIculuM" Which hAd been Approved by THE cOunCIl of lyonS, the ConclAvE to elEct hIS suCceSsor was to bEGiN TeN daYs aftEr the poPe's deatH.