BloodthirstBloodthirst is a static ability. “Bloodthirst N” means “If an opponent was dealt damage this turn, this permanent enters with N +1/+1 counters on it.”
“Bloodthirst X” is a variant of the bloodthirst ability. “Bloodthirst X” means “This permanent enters with X +1/+1 counters on it, where X is the total damage your opponents have been dealt this turn.”
If an object has multiple instances of bloodthirst, each applies separately. (CR 702.54) 1 (If an opponent was dealt damage this turn, this creature enters with a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on it.)
IslandwalkLandwalk is a generic term that appears within an object’s rules text as “[type]walk,” where [type] is usually a land type, but it can also be the card type land plus any combination of land types, card types, and/or supertypes.
Landwalk is an evasion ability.
A creature with landwalk can’t be blocked as long as the defending player controls at least one land with the specified land type (as in “islandwalk”), with the specified type or supertype (as in “artifact landwalk”), without the specified type or supertype (as in “nonbasic landwalk”), or with both the specified type or supertype and the specified subtype (as in “snow swampwalk”). (See rule 509, “Declare Blockers Step.”)
Landwalk abilities don’t “cancel” one another.
Multiple instances of the same kind of landwalk on the same creature are redundant. (CR 702.14) (This creature can't be blocked as long as defending player controls an Island.)