The Watcher in the Water enters tapped with nine stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Whenever you draw a card during an opponent's turn, create a 1/1 blue Tentacle creature token.
Whenever a Tentacle you control dies, untap up to one target Kraken and put a stun counter on up to one target nonland permanent.
The Watcher enters tapped under nine stun counters, so it's a passive engine rather than an early beater—you load up on instant-speed and opponent-turn card draw to flood the board with 1/1 Tentacles. Sacrificing or trading Tentacles untaps the Watcher (shedding stun counters) while stunning down opponents' key permanents, locking them out turn after turn. You grind value with draw, control the board with repeated stun-tapping, then close with a swarm of tokens or a finisher.
Generates a steady stream of free tokens just by drawing on opponents' turns
Built-in soft removal/lockdown by stacking stun counters on threats and lands each turn
Mono-blue gives access to the best counterspells, card draw, and protection
Token swarm enables sacrifice synergies, blink, and go-wide payoffs
Enters tapped with nine stun counters, so it does nothing the turn it lands and is slow to free up
Token generation only triggers on opponents' turns, requiring instant-speed draw to be reliable
Mono-blue lacks efficient creature removal and life gain
Heavily reliant on the commander; if it's repeatedly removed the engine stalls
Cheats the Watcher in untapped, bypassing the nine stun counters entirely.
Add more instant-speed and opponent-turn draw doublers (Teferi's Ageless Insight, Alrund's Epiphany loops) plus free sacrifice outlets like Ashnod's Altar and Phyrexian Altar to weaponize the death trigger. Include ways to cheat the Watcher into play untapped or remove its stun counters faster, and stronger interaction (Cyclonic Rift, Force of Will) to protect the engine. To push to cEDH, lean into a tight stun-lock combined with card-advantage engines and a compact win like Thassa's Oracle backed by tutors.