INDENTURE SUPPLEMENT

Exhibit 4.2

DISCOVER CARD EXECUTION NOTE TRUST

Issuer

and

U.S. BANK NATIONAL ASSOCIATION

Indenture Trustee

CLASS C(2008-3) TERMS DOCUMENT

Dated as of August 28, 2008

to

INDENTURE SUPPLEMENT

Dated as of July 26, 2007

for the DiscoverSeries Notes

to

INDENTURE

Dated as of July 26, 2007

TABLE OF CONTENTS

THIS CLASS C(2008-3) TERMS DOCUMENT (this “ Terms Document ”), by and between DISCOVER CARD EXECUTION NOTE TRUST, a statutory trust created under the laws of the State of Delaware (the “ Issuer ”), and U.S. BANK NATIONAL ASSOCIATION, a national banking association organized and existing under the laws of the United States of America, as Indenture Trustee (the “ Indenture Trustee ”), is made and entered into as of August 28, 2008.

Pursuant to this Terms Document, the Issuer shall create a new Tranche of Class C Notes of the DiscoverSeries and shall specify the principal terms thereof.

ARTICLE I

Definitions and Other Provisions of General Application

Section 1.01. Definitions . For all purposes of this Terms Document, except as otherwise expressly provided or unless the context otherwise requires:

(1) the terms defined in this Article have the meanings assigned to them in this Article, and include the plural as well as the singular;

(2) all other terms used herein which are defined in the Indenture Supplement or the Indenture, either directly or by reference therein, have the meanings assigned to them therein;

(3) all accounting terms not otherwise defined herein have the meanings assigned to them in accordance with generally accepted accounting principles and, except as otherwise herein expressly provided, the term “generally accepted accounting principles” with respect to any computation required or permitted hereunder means such accounting principles as are generally accepted in the United States of America at the date of such computation;

(4) all references in this Terms Document to designated “Articles,” “Sections” and other subdivisions are to the designated Articles, Sections and other subdivisions of this Terms Document; The words “herein,” “hereof” and “hereunder” and other words of similar import refer to this Terms Document as a whole and not to any particular Article, Section or other subdivision;

(5) in the event that any term or provision contained herein shall conflict with or be inconsistent with any term or provision contained in the Indenture Supplement or the Indenture, the terms and provisions of this Terms Document shall be controlling, but solely with respect to the Class C(2008-3) Notes;

(6) each capitalized term defined herein shall relate only to the Class C(2008-3) Notes and no other Tranche of Notes issued by the Issuer;

(7) “including” and words of similar import will be deemed to be followed by “without limitation”; and

(8) for purposes of determining any amount or making any calculation hereunder, such amount or calculation, (x) if specified to be as of the first day of any Due Period, shall (a)

include any Notes issued during such Due Period as if such Notes had been outstanding on the first day of such Due Period and (b) give effect to any payments, deposits or other allocations made on the Distribution Date related to the prior Due Period, and (y) if specified to be as of the close of business on the last day of any Due Period shall give effect to any payments, deposits or other allocations made on the related Distribution Date.

“ Accumulation Amount ” means $8,750,000; provided , however , if the commencement of the Accumulation Period is delayed in accordance with Section 4.02 of the Indenture Supplement, the Accumulation Amount shall be determined in accordance with the definition of “Accumulation Amount” in the Indenture Supplement.

“ Accumulation Commencement Date ” means August 1, 2009 (or, if such day is not a Business Day, the next succeeding Business Day), or such later date as the Calculation Agent on behalf of the Issuer determines in accordance with Section 4.02 of the Indenture Supplement.

“ Accumulation Period ” has the meaning set forth in the Indenture Supplement.

“ Accumulation Period Length ” means 12 months; provided , however , if the commencement of the Accumulation Period is delayed in accordance with Section 4.02 of the Indenture Supplement, the Accumulation Period Length shall be determined in accordance with the definition of “Accumulation Period Length” in the Indenture Supplement.

“ Accumulation Reserve Funding Period ” shall not apply if the Calculation Agent on behalf of the Issuer notifies the Indenture Trustee that it expects the Accumulation Period Length to be adjusted to one (1) month, and otherwise shall mean a period commencing on the first Distribution Date on which a condition in the right column of the following table was in effect on the immediately preceding Distribution Date, if the Distribution Date is a Distribution Date described in the corresponding left column of the following table, and ending on the Distribution Date immediately preceding the earlier to occur of:

(x) the Expected Maturity Date for the Class C(2008-3) Notes and

(y) the Principal Payment Date on which the Outstanding Dollar Principal Amount of the Class C(2008-3) Notes is paid in full.

2

“ Class C(2008-3) Adverse Event ” means the occurrence of any of the following: (a) an Early Redemption Event with respect to the Class C(2008-3) Notes or (b) an Event of Default and acceleration of the Class C(2008-3) Notes; provided , however , that if the only such event to have occurred is an Excess Spread Early Redemption Event for which an Excess Spread Early Redemption Cure has occurred, a Class C(2008-3) Adverse Event shall not be treated as continuing from and after the date of such cure.

“ Class C(2008-3) Note ” means any Note, in the form set forth in Exhibit A hereto, designated therein as a Class C(2008-3) Note and duly executed and authenticated in accordance with the Indenture.

“ Class C(2008-3) Noteholder ” means a Person in whose name a Class C(2008-3) Note is registered in the Note Register.

“ Class C(2008-3) Termination Date ” means the earliest to occur of (a) the Principal Payment Date on which the Outstanding Dollar Principal Amount of the Class C(2008-3) Notes is paid in full, (b) the Legal Maturity Date and (c) the date on which the Indenture is discharged and satisfied pursuant to Article VI thereof.

“ Class C Reserve Account Percentage ” means, for any Distribution Date on which a condition in the left column of the following table was in effect on the immediately preceding Distribution Date, the percentage in the corresponding right column of the following table (or if more than one conditions were in effect on the immediately preceding Distribution Date, the largest percentage).

3

“ Excess Spread Percentage ” for any Distribution Date means a fraction, the numerator of which is the Excess Spread Amount for such Distribution Date multiplied by 12 and the denominator of which is the sum of the Nominal Liquidation Amounts of all Tranches of DiscoverSeries Notes as of the first day of the related Due Period.

“ Expected Maturity Date ” means August 16, 2010.

“ Indenture ” means the Indenture dated as of July 26, 2007 between the Issuer and Indenture Trustee, as the same may be amended, supplemented, restated, amended and restated, replaced or otherwise modified from time to time.

“ Indenture Supplement ” means the Indenture Supplement dated as of July 26, 2007 for the DiscoverSeries Notes, by and between the Issuer and the Indenture Trustee, as the same may be amended, supplemented, restated, amended and restated, replaced or otherwise modified from time to time.

“ Initial Dollar Principal Amount ” means $105,000,000, or such higher amount as is specified in any Notice of Additional Issuance under Section 2.09.

“ Interest Accrual Period ” means, with respect to any Interest Payment Date, the period from and including the previous Interest Payment Date (or, in the case of the first Interest Payment Date for any Class C(2008-3) Note, from and including the applicable Issuance Date) to but excluding such Interest Payment Date.

4

“ Interest Payment Date ” means the fifteenth day of each month commencing in September 2008, or if such fifteenth day is not a Business Day, the next succeeding Business Day.

“ Issuance Date ” means August 28, 2008 with respect to all Class C(2008-3) Notes issued on the date hereof and, with respect to any additional Class C(2008-3) Notes issued pursuant to Section 2.09, any Issuance Date specified in the Notice of Additional Issuance delivered thereunder.

“ Legal Maturity Date ” means February 15, 2013.

“ LIBOR ” means, with respect to any LIBOR Determination Date, the rate for deposits in United States dollars with a duration comparable to the relevant Interest Accrual Period which appears on Reuters Screen LIBOR01 as of 11:00 a.m., London time, on such day. If such rate does not appear on Reuters Screen LIBOR01, the rate will be determined by the Indenture Trustee on the basis of the rates at which deposits in United States dollars are offered by major banks in the London interbank market, selected by the Indenture Trustee, at approximately 11:00 a.m., London time, on such day to prime banks in the London interbank market with a duration comparable to the relevant Interest Accrual Period commencing on that day. The Indenture Trustee will request the principal London office of at least four banks to provide a quotation of its rate. If at least two such quotations are provided, the rate will be the arithmetic mean of the quotations. If fewer than two quotations are provided as requested, the rate for that day will be the arithmetic mean of the rates quoted by four major banks in New York City, selected by the Trustee, at approximately 11:00 a.m., New York City time, on that day for loans i