Conflux

This land enters tapped. T: Add U. Transmute 1UU (1UU, Discard this card: Search your library for a card with mana value 0, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

(2/B can be paid with any two mana or with B. This card's mana value is 6.) Search your library for a card with mana value less than or equal to the number of lands you control, reveal it, put it into your hand, then shuffle.

Add BBB. Threshold — Add BBBBB instead if there are seven or more cards in your graveyard.

Dark Depths enters with ten ice counters on it. 3: Remove an ice counter from Dark Depths. When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

First strike, deathtouch Whenever a creature an opponent controls dies, you may return target artifact card from your graveyard to your hand.

1, T: Exile target creature you control. 7, T: Exile target creature you don't control. When Helvault is put into a graveyard from the battlefield, return all cards exiled with it to the battlefield under their owners' control.

1UU: Target permanent becomes an artifact in addition to its other types. (This effect lasts indefinitely.) 3U: Gain control of target artifact. (This effect lasts indefinitely.)

Shuffle your library. Then exile the top card of your library. Until end of turn, you may play that card without paying its mana cost. Storm (When you cast this spell, copy it for each spell cast before it this turn.)