Because of the lengthy discussions in the "TPS thread"* it might be worth it to discuss Gifts Ungiven as 5th and possibly 6th Infernal Tutor in this deck using its current skeleton without adding extra cards like Reforge the Soul.
If we consider 15 lands, 16 mana, 12 cantrips incl Probe, 4 Tutor, 1 ToA, 1 PiF, 6 Discard as fixed we have 5 flex slots left in the deck. 4-5 of these are filled with business spells & cantrips and there sometimes is a 7th protection spell. The options for the extra business/cantrips slots currently are: (1) Preordain (up to 4), (2) Grim Tutor (up to 2), (3) Lim-Dul's Vault (up to 2), (4) Ad Nauseam (#1 and rarely #2), (5) Empty the Warrens, (6) Past in Flames #2.
The previously mentioned thread brings forth Gifts Ungiven as an additional option for these slots and I feel it warrants testing in the proper frame. The idea is that you mainly use Gifts to go for a PiF kill, and sometimes use it for setup.
A quick glance gives me this impression: (please correct this if there are better options)
Gifts for PiF: 6URB (9), 4+ Spells cast, 1+ Life.
Have 3U + 3R + B and 4 spells played this turn.
Gifts for IT+PiF+DR+CR, float 3R+B
Get IT+PiF, cast PiF, float B
Flash back DR, CR (threshed) and cast IT from hand into ToA.
Grim Tutor for PiF: 4RBBB (8), ~3+ spells cast, 7+ Life.
Have BB1+3R+B,
Cast Grim Tutor for PiF, float 3RB
Cast PiF, float B
Flashback Rituals and Grim Tutor for ToA
Summarized:
Gifts costs a mana more (9 instead of 8).
GT can be more expensive depending on the amount of rituals available post-PiF (just DR and CR with thresh makes it already cost an extra mana)
Gifts has less problems regarding the anti-synergy of LED and PiF since you tutor up two rituals to flashback.
Gifts costs 3 or 6 life less.
Gifts becomes cheaper with a good graveyard (IT in the GY makes Gifts cost 7 mana, where GT is still 8)
Gifts might require more cards already in the yard, as CR almost always needs to be threshed.
GT finds any card in set-up, and is one cheaper as a setup spell.
Gifts has some setup applications (e.g. finding Duress/Therapy/Thoughtseize/X), finding you two cards.
Gifts is one more damage for Ad Nauseam, while GT costs 3 life to cast after Ad Nauseam. -> Might want to play MD Empty if you go for Gifts.
Snapcaster Mage might be worth testing as well if you do include Gifts.
Gifts makes the deck even more graveyard-reliant, but you can side them out and go for Ad Nauseam/Empty postboard if required.
Has anyone tested such a list? For example filling the 5 flex slots with: (1) Empty the Warrens, (2) Gifts Ungiven, (3) Gifts Ungiven/Top/Preordain, (4) 7th discard spell, probably the 1st Thoughtseize and (5) Top/Preordain/SCM?
*See:
http://www.mtgthesource.com/forums/s...660-Legacy-TPS