DeathtouchDeathtouch is a static ability.
A creature with toughness greater than 0 that’s been dealt damage by a source with deathtouch since the last time state-based actions were checked is destroyed as a state-based action. See rule 704.
Any nonzero amount of combat damage assigned to a creature by a source with deathtouch is considered to be lethal damage for the purposes of determining if excess damage is being dealt.
The deathtouch rules function no matter what zone an object with deathtouch deals damage from.
If an object is no longer in the zone it’s expected to be in as an effect causes it to deal damage, its last known information is used to determine whether it had deathtouch.
Multiple instances of deathtouch on the same object are redundant. (CR 702.2)
Face-down creatures you control have "
: Turn this creature face up. If you can't,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) it, then you may
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) the exiled card without paying its mana cost."
Whenever an Assassin you control deals combat damage to an opponent,
cloakTo cloak a card, turn it face down. It becomes a 2/2 face-down creature card with ward , no name, no subtypes, and no mana cost. Put that card onto the battlefield face down. That permanent is a cloaked permanent for as long as it remains face down. The effect defining its characteristics works while the card is face down and ends when it’s turned face up.
Any time you have priority, you may turn a cloaked permanent you control face up. This is a special action that doesn’t use the stack (see rule 116.2b). To do this, show all players that the card representing that permanent is a creature card and what that card’s mana cost is, pay that cost, then turn the permanent face up. The effect defining its characteristics while it was face down ends, and it regains its normal characteristics. (If the card representing that permanent isn’t a creature card or it doesn’t have a mana cost, it can’t be turned face up this way.)
If a card with morph is cloaked, its controller may turn that card face up using either the procedure described in rule 702.37e to turn a face-down permanent with morph face up or the procedure described above to turn a cloaked permanent face up.
If a card with disguise is cloaked, its controller may turn that card face up using either the procedure described in rule 702.168d to turn a face-down permanent with disguise face up or the procedure described above to turn a cloaked permanent face up.
If an effect instructs a player to cloak multiple cards from a single library, those cards are cloaked one at a time.
If an effect instructs a player to cloak a card and a rule or effect prohibits the face-down object from entering the battlefield, that card isn’t cloaked. Its characteristics remain unmodified and it remains in its previous zone. If it was face up, it remains face up.
If a cloaked permanent that’s represented by an instant or sorcery card would turn face up, its controller reveals it and leaves it face down. Abilities that trigger whenever a permanent is turned face up won’t trigger.
See rule 708, “Face-Down Spells and Permanents,” for more information. (CR 701.58) the top card of that player's library.