<?xml version="1.0"?>
<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><infoTable><nameOfIssuer>AETNA INC NEW</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>00817Y108</cusip><value>29350</value><shrsOrPrnAmt><sshPrnamt>245200</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>245200</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>ALIBABA GROUP HLDG LTD</nameOfIssuer><titleOfClass>SPONSORED ADS</titleOfClass><cusip>01609W102</cusip><value>15976</value><shrsOrPrnAmt><sshPrnamt>202300</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>202300</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>AUTODESK INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>052769106</cusip><value>22028</value><shrsOrPrnAmt><sshPrnamt>417200</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>417200</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>BALL CORP</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>058498106</cusip><value>40742</value><shrsOrPrnAmt><sshPrnamt>581606</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>581606</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>BALL CORP</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>058498106</cusip><value>17393</value><shrsOrPrnAmt><sshPrnamt>248300</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>248300</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>BIOGEN INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>09062X103</cusip><value>21783</value><shrsOrPrnAmt><sshPrnamt>90000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>90000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>CATERPILLAR INC DEL</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>149123101</cusip><value>22314</value><shrsOrPrnAmt><sshPrnamt>300000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Put</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>300000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>CHUBB LIMITED</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>H1467J104</cusip><value>22577</value><shrsOrPrnAmt><sshPrnamt>175000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>175000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>E M C CORP MASS</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>268648102</cusip><value>176506</value><shrsOrPrnAmt><sshPrnamt>6467806</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>6467806</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>ENERGY TRANSFER EQUITY L P</nameOfIssuer><titleOfClass>COM UT LTD PTN</titleOfClass><cusip>29273V100</cusip><value>6691</value><shrsOrPrnAmt><sshPrnamt>474200</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>474200</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>FEDERAL NATION MOR  8.25% SRS S PRF</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>313586752</cusip><value>27873</value><shrsOrPrnAmt><sshPrnamt>6221623</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>6221623</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>GLOBALSTAR INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>378973408</cusip><value>5450</value><shrsOrPrnAmt><sshPrnamt>5000000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>5000000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>HUMANA INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>444859102</cusip><value>109730</value><shrsOrPrnAmt><sshPrnamt>619209</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>619209</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>HUMANA INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>444859102</cusip><value>29240</value><shrsOrPrnAmt><sshPrnamt>165000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>165000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>HUMANA INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>444859102</cusip><value>88587</value><shrsOrPrnAmt><sshPrnamt>499900</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Put</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>499900</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>IMPERVA INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>45321L100</cusip><value>9670</value><shrsOrPrnAmt><sshPrnamt>227098</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>227098</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>INFOBLOX INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>45672H104</cusip><value>14338</value><shrsOrPrnAmt><sshPrnamt>775000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>775000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>LIBERTY MEDIA CORP DELAWARE</nameOfIssuer><titleOfClass>COM C BRAVES GRP</titleOfClass><cusip>531229888</cusip><value>10156</value><shrsOrPrnAmt><sshPrnamt>685272</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>685272</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>LIBERTY TRIPADVISOR HLDGS IN</nameOfIssuer><titleOfClass>COM SER A</titleOfClass><cusip>531465102</cusip><value>35844</value><shrsOrPrnAmt><sshPrnamt>1659423</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>1659423</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>MARKETO INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>57063L107</cusip><value>3499</value><shrsOrPrnAmt><sshPrnamt>100000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Put</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>100000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>MEDIA GEN INC NEW</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>58441K100</cusip><value>80037</value><shrsOrPrnAmt><sshPrnamt>4741520</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>4741520</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>MEDIVATION INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>58501N101</cusip><value>21153</value><shrsOrPrnAmt><sshPrnamt>342500</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>342500</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>MONSANTO CO NEW</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>61166W101</cusip><value>35088</value><shrsOrPrnAmt><sshPrnamt>350000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>350000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>OFFICE DEPOT INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>676220106</cusip><value>19022</value><shrsOrPrnAmt><sshPrnamt>5907400</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>5907400</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>PFIZER INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>717081103</cusip><value>148049</value><shrsOrPrnAmt><sshPrnamt>4134300</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Put</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>4134300</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>POWERSHARES QQQ TRUST</nameOfIssuer><titleOfClass>UNIT SER 1</titleOfClass><cusip>73935A104</cusip><value>89288</value><shrsOrPrnAmt><sshPrnamt>831200</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Put</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>831200</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>SIGA TECHNOLOGIES ORD</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>826917106</cusip><value>7136</value><shrsOrPrnAmt><sshPrnamt>4955721</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>4955721</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>SPDR S&amp;P 500 ETF TR</nameOfIssuer><titleOfClass>TR UNIT</titleOfClass><cusip>78462F103</cusip><value>36430</value><shrsOrPrnAmt><sshPrnamt>174800</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>174800</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>STARWOOD HOTELS&amp;RESORTS WRLD</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>85590A401</cusip><value>114263</value><shrsOrPrnAmt><sshPrnamt>1532499</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>1532499</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>SYNGENTA AG</nameOfIssuer><titleOfClass>SPONSORED ADR</titleOfClass><cusip>87160A100</cusip><value>130516</value><shrsOrPrnAmt><sshPrnamt>1724118</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>1724118</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>TUMI HLDGS INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>89969Q104</cusip><value>22038</value><shrsOrPrnAmt><sshPrnamt>823560</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>823560</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>TYCO INTL PLC</nameOfIssuer><titleOfClass>SHS</titleOfClass><cusip>G91442106</cusip><value>13805</value><shrsOrPrnAmt><sshPrnamt>331928</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>331928</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>YAHOO INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>984332106</cusip><value>105639</value><shrsOrPrnAmt><sshPrnamt>2817036</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>2817036</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable><infoTable><nameOfIssuer>YAHOO INC</nameOfIssuer><titleOfClass>COM</titleOfClass><cusip>984332106</cusip><value>12975</value><shrsOrPrnAmt><sshPrnamt>346000</sshPrnamt><sshPrnamtType>SH</sshPrnamtType></shrsOrPrnAmt><putCall>Call</putCall><investmentDiscretion>DFND</investmentDiscretion><otherManager>
		</otherManager><votingAuthority><Sole>346000</Sole><Shared>0</Shared><None>0</None></votingAuthority></infoTable></informationTable>
